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diff --git a/doc/rfc/rfc7707.txt b/doc/rfc/rfc7707.txt new file mode 100644 index 0000000..9fc86f2 --- /dev/null +++ b/doc/rfc/rfc7707.txt @@ -0,0 +1,2131 @@ + + + + + + +Internet Engineering Task Force (IETF) F. Gont +Request for Comments: 7707 Huawei Technologies +Obsoletes: 5157 T. Chown +Category: Informational Jisc +ISSN: 2070-1721 March 2016 + + + Network Reconnaissance in IPv6 Networks + +Abstract + + IPv6 offers a much larger address space than that of its IPv4 + counterpart. An IPv6 subnet of size /64 can (in theory) accommodate + approximately 1.844 * 10^19 hosts, thus resulting in a much lower + host density (#hosts/#addresses) than is typical in IPv4 networks, + where a site typically has 65,000 or fewer unique addresses. As a + result, it is widely assumed that it would take a tremendous effort + to perform address-scanning attacks against IPv6 networks; therefore, + IPv6 address-scanning attacks have been considered unfeasible. This + document formally obsoletes RFC 5157, which first discussed this + assumption, by providing further analysis on how traditional address- + scanning techniques apply to IPv6 networks and exploring some + additional techniques that can be employed for IPv6 network + reconnaissance. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7707. + + + + + + + + + + + +Gont & Chown Informational [Page 1] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +Copyright Notice + + Copyright (c) 2016 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. Requirements for the Applicability of Network Reconnaissance + Techniques . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 4. IPv6 Address Scanning . . . . . . . . . . . . . . . . . . . . 6 + 4.1. Address Configuration in IPv6 . . . . . . . . . . . . . . 6 + 4.1.1. Stateless Address Autoconfiguration (SLAAC) . . . . . 6 + 4.1.2. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) 11 + 4.1.3. Manually Configured Addresses . . . . . . . . . . . . 12 + 4.1.4. IPv6 Addresses Corresponding to + Transition/Coexistence Technologies . . . . . . . . . 14 + 4.1.5. IPv6 Address Assignment in Real-World Network + Scenarios . . . . . . . . . . . . . . . . . . . . . . 14 + 4.2. IPv6 Address Scanning of Remote Networks . . . . . . . . 17 + 4.2.1. Reducing the Subnet ID Search Space . . . . . . . . . 18 + 4.3. IPv6 Address Scanning of Local Networks . . . . . . . . . 19 + 4.4. Existing IPv6 Address-Scanning Tools . . . . . . . . . . 20 + 4.4.1. Remote IPv6 Network Address Scanners . . . . . . . . 20 + 4.4.2. Local IPv6 Network Address Scanners . . . . . . . . . 21 + 4.5. Mitigations . . . . . . . . . . . . . . . . . . . . . . . 21 + 4.6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . 22 + 5. Alternative Methods to Glean IPv6 Addresses . . . . . . . . . 23 + 5.1. Leveraging the Domain Name System (DNS) for Network + Reconnaissance . . . . . . . . . . . . . . . . . . . . . 23 + 5.1.1. DNS Advertised Hosts . . . . . . . . . . . . . . . . 23 + 5.1.2. DNS Zone Transfers . . . . . . . . . . . . . . . . . 23 + 5.1.3. DNS Brute Forcing . . . . . . . . . . . . . . . . . . 23 + 5.1.4. DNS Reverse Mappings . . . . . . . . . . . . . . . . 24 + 5.2. Leveraging Local Name Resolution and Service Discovery + Services . . . . . . . . . . . . . . . . . . . . . . . . 24 + 5.3. Public Archives . . . . . . . . . . . . . . . . . . . . . 25 + + + +Gont & Chown Informational [Page 2] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + 5.4. Application Participation . . . . . . . . . . . . . . . . 25 + 5.5. Inspection of the IPv6 Neighbor Cache and Routing Table . 25 + 5.6. Inspection of System Configuration and Log Files . . . . 26 + 5.7. Gleaning Information from Routing Protocols . . . . . . . 26 + 5.8. Gleaning Information from IP Flow Information Export + (IPFIX) . . . . . . . . . . . . . . . . . . . . . . . . . 26 + 5.9. Obtaining Network Information with traceroute6 . . . . . 26 + 5.10. Gleaning Information from Network Devices Using SNMP . . 27 + 5.11. Obtaining Network Information via Traffic Snooping . . . 27 + 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 27 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 27 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 28 + 8.2. Informative References . . . . . . . . . . . . . . . . . 29 + Appendix A. Implementation of a Full-Fledged IPv6 Address- + Scanning Tool . . . . . . . . . . . . . . . . . . . 34 + A.1. Host-Probing Considerations . . . . . . . . . . . . . . . 34 + A.2. Implementation of an IPv6 Local Address-Scanning Tool . . 35 + A.3. Implementation of an IPv6 Remote Address-Scanning Tool . 36 + Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 37 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38 + +1. Introduction + + The main driver for IPv6 [RFC2460] deployment is its larger address + space [CPNI-IPv6]. This larger address space not only allows for an + increased number of connected devices but also introduces a number of + subtle changes in several aspects of the resulting networks. One of + these changes is the reduced host density (the number of hosts + divided by the number of addresses) of typical IPv6 subnetworks, when + compared to their IPv4 counterparts. [RFC5157] describes how this + significantly lower IPv6 host density is likely to make classic + network address-scanning attacks less feasible, since even by + applying various heuristics, the address space to be scanned remains + very large. RFC 5157 goes on to describe some alternative methods + for attackers to glean active IPv6 addresses and provides some + guidance for administrators and implementors, e.g., not using + sequential addresses with DHCPv6. + + With the benefit of more than five years of additional IPv6 + deployment experience, this document formally obsoletes RFC 5157. It + emphasizes that while address-scanning attacks are less feasible, + they may, with appropriate heuristics, remain possible. At the time + that RFC 5157 was written, observed address-scanning attacks were + typically across ports on the addresses of discovered servers; since + then, evidence that some classic address scanning is occurring is + being witnessed. This text thus updates the analysis on the + feasibility of address-scanning attacks in IPv6 networks, and it + + + +Gont & Chown Informational [Page 3] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + explores a number of additional techniques that can be employed for + IPv6 network reconnaissance. Practical examples and guidance are + also included in the appendices. + + On one hand, raising awareness about IPv6 network reconnaissance + techniques may allow (in some cases) network and security + administrators to prevent or detect such attempts. On the other + hand, network reconnaissance is essential for the so-called + "penetration tests" typically performed to assess the security of + production networks. As a result, we believe the benefits of a + thorough discussion of IPv6 network reconnaissance are twofold. + + Section 4 analyzes the feasibility of address-scanning attacks (e.g., + ping sweeps) in IPv6 networks and explores a number of possible + improvements to such techniques. Appendix A describes how the + aforementioned analysis can be leveraged to produce address-scanning + tools (e.g., for penetration testing purposes). Finally, the rest of + this document discusses a number of miscellaneous techniques that + could be leveraged for IPv6 network reconnaissance. + +2. Conventions + + Throughout this document, we consider that bits are numbered from + left to right, starting at 0, and that bytes are numbered from left + to right, starting at 0. + +3. Requirements for the Applicability of Network Reconnaissance + Techniques + + Throughout this document, a number of network reconnaissance + techniques are discussed. Each of these techniques has different + requirements on the side of the practitioner, with respect to whether + they require local access to the target network and whether they + require login access (or similar access credentials) to the system on + which the technique is applied. + + The following table tries to summarize the aforementioned + requirements and serves as a cross index to the corresponding + sections. + + + + + + + + + + + + +Gont & Chown Informational [Page 4] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + +---------------------------------------------+----------+----------+ + | Technique | Local | Login | + | | access | access | + +---------------------------------------------+----------+----------+ + | Remote Address Scanning (Section 4.2) | No | No | + +---------------------------------------------+----------+----------+ + | Local Address Scanning (Section 4.3) | Yes | No | + +---------------------------------------------+----------+----------+ + | DNS Advertised Hosts (Section 5.1.1) | No | No | + +---------------------------------------------+----------+----------+ + | DNS Zone Transfers (Section 5.1.2) | No | No | + +---------------------------------------------+----------+----------+ + | DNS Brute Forcing (Section 5.1.3) | No | No | + +---------------------------------------------+----------+----------+ + | DNS Reverse Mappings (Section 5.1.4) | No | No | + +---------------------------------------------+----------+----------+ + | Leveraging Local Name Resolution and | Yes | No | + | Service Discovery Services (Section 5.2) | | | + +---------------------------------------------+----------+----------+ + | Public Archives (Section 5.3) | No | No | + +---------------------------------------------+----------+----------+ + | Application Participation (Section 5.4) | No | No | + +---------------------------------------------+----------+----------+ + | Inspection of the IPv6 Neighbor Cache and | No | Yes | + | Routing Table (Section 5.5) | | | + +---------------------------------------------+----------+----------+ + | Inspecting System Configuration and Log | No | Yes | + | Files (Section 5.6) | | | + +---------------------------------------------+----------+----------+ + | Gleaning Information from Routing Protocols | Yes | No | + | (Section 5.7) | | | + +---------------------------------------------+----------+----------+ + | Gleaning Information from IP Flow | No | Yes | + | Information Export (IPFIX) (Section 5.8) | | | + +---------------------------------------------+----------+----------+ + | Obtaining Network Information with | No | No | + | traceroute6 (Section 5.9) | | | + +---------------------------------------------+----------+----------+ + | Gleaning Information from Network Devices | No | Yes | + | Using SNMP (Section 5.10) | | | + +---------------------------------------------+----------+----------+ + | Obtaining Network Information via Traffic | Yes | No | + | Snooping (Section 5.11) | | | + +---------------------------------------------+----------+----------+ + + Table 1: Requirements for the Applicability of + Network Reconnaissance Techniques + + + + +Gont & Chown Informational [Page 5] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +4. IPv6 Address Scanning + + This section discusses how traditional address-scanning techniques + (e.g., "ping sweeps") apply to IPv6 networks. Section 4.1 provides + an essential analysis of how address configuration is performed in + IPv6, identifying patterns in IPv6 addresses that can be leveraged to + reduce the IPv6 address search space when performing IPv6 address- + scanning attacks. Section 4.2 discusses IPv6 address scanning of + remote networks. Section 4.3 discusses IPv6 address scanning of + local networks. Section 4.4 discusses existing IPv6 address-scanning + tools. Section 4.5 provides advice on how to mitigate IPv6 address- + scanning attacks. Finally, Appendix A discusses how the insights + obtained in the following subsections can be incorporated into a + fully fledged IPv6 address-scanning tool. + +4.1. Address Configuration in IPv6 + + IPv6 incorporates two automatic address-configuration mechanisms: + Stateless Address Autoconfiguration (SLAAC) [RFC4862] and Dynamic + Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315]. Support for + SLAAC for automatic address configuration is mandatory, while support + for DHCPv6 is optional -- however, most current versions of general- + purpose operating systems support both. In addition to automatic + address configuration, hosts, typically servers, may employ manual + configuration, in which all the necessary information is manually + entered by the host or network administrator into configuration files + at the host. + + The following subsections describe each of the possible configuration + mechanisms/approaches in more detail. + +4.1.1. Stateless Address Autoconfiguration (SLAAC) + + The basic idea behind SLAAC is that every host joining a network will + send a multicasted solicitation requesting network configuration + information, and local routers will respond to the request providing + the necessary information. SLAAC employs two different ICMPv6 + message types: ICMPv6 Router Solicitation and ICMPv6 Router + Advertisement messages. Router Solicitation messages are employed by + hosts to query local routers for configuration information, while + Router Advertisement messages are employed by local routers to convey + the requested information. + + + + + + + + + +Gont & Chown Informational [Page 6] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Router Advertisement messages convey a plethora of network + configuration information, including the IPv6 prefix that should be + used for configuring IPv6 addresses on the local network. For each + local prefix learned from a Router Advertisement message, an IPv6 + address is configured by appending a locally generated Interface + Identifier (IID) to the corresponding IPv6 prefix. + + The following subsections describe currently deployed policies for + generating the IIDs used with SLAAC. + +4.1.1.1. Interface Identifiers Embedding IEEE Identifiers + + The traditional SLAAC IIDs are based on the link-layer address of the + corresponding network interface card. For example, in the case of + Ethernet addresses, the IIDs are constructed as follows: + + 1. The "Universal" bit (bit 6, from left to right) of the address is + set to 1. + + 2. The word 0xfffe is inserted between the Organizationally Unique + Identifier (OUI) and the rest of the Ethernet address. + + For example, the Media Access Control (MAC) address 00:1b:38:83:88:3c + would lead to the IID 021b:38ff:fe83:883c. + + A number of considerations should be made about these identifiers. + Firstly, one 16-bit word (bytes 3-4) of the resulting address always + has a fixed value (0xfffe), thus reducing the search space for the + IID. Secondly, the high-order three bytes of the IID correspond to + the OUI of the network interface card vendor. Since not all possible + OUIs have been assigned, this further reduces the IID search space. + Furthermore, of the assigned OUIs, many could be regarded as + corresponding to legacy devices and thus are unlikely to be used for + Internet-connected IPv6-enabled systems, yet further reducing the IID + search space. Finally, in some scenarios, it could be possible to + infer the OUI in use by the target network devices, yet narrowing + down the possible IIDs even more. + + NOTE: + For example, an organization known for being provisioned by vendor + X is likely to have most of the nodes in its organizational + network with OUIs corresponding to vendor X. + + These considerations mean that in some scenarios, the original IID + search space of 64 bits may be effectively reduced to 2^24 or n * + 2^24 (where "n" is the number of different OUIs assigned to the + target vendor). + + + + +Gont & Chown Informational [Page 7] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Furthermore, if just one host address is detected or known within a + subnet, it is not unlikely that, if systems were ordered in a batch, + they may have sequential MAC addresses. Additionally, given a MAC + address observed in one subnet, sequential or nearby MAC addresses + may be seen in other subnets in the same site. + + NOTE: + [RFC7136] notes that all bits of an IID should be treated as + "opaque" bits. Furthermore, [DEFAULT-IIDS] is currently in the + process of changing the default IID generation scheme to align + with [RFC7217] (as described below in Section 4.1.1.5), such that + IIDs are semantically opaque and do not follow any patterns. + Therefore, the traditional IIDs based on link-layer addresses are + expected to become less common over time. + +4.1.1.2. Interface Identifiers of Virtualization Technologies + + IIDs resulting from virtualization technologies can be considered a + specific subcase of IIDs embedding IEEE identifiers (please see + Section 4.1.1.1): they employ IEEE identifiers, but part of the IID + has specific patterns. The following subsections describe IIDs of + some popular virtualization technologies. + +4.1.1.2.1. VirtualBox + + All automatically generated MAC addresses in VirtualBox virtual + machines employ the OUI 08:00:27 [VBox2011]. This means that all + addresses resulting from traditional SLAAC will have an IID of the + form a00:27ff:feXX:XXXX, thus effectively reducing the IID search + space from 64 bits to 24 bits. + +4.1.1.2.2. VMware ESX Server + + The VMware ESX server (versions 1.0 to 2.5) provides yet a more + interesting example. Automatically generated MAC addresses have the + following pattern [vmesx2011]: + + 1. The OUI is set to 00:05:69. + + 2. The next 16 bits of the MAC address are set to the same value as + the last 16 bits of the console operating system's primary IPv4 + address. + + 3. The final 8 bits of the MAC address are set to a hash value based + on the name of the virtual machine's configuration file. + + + + + + +Gont & Chown Informational [Page 8] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + This means that, assuming the console operating system's primary IPv4 + address is known, the IID search space is reduced from 64 bits to 8 + bits. + + On the other hand, manually configured MAC addresses in the VMware + ESX server employ the OUI 00:50:56, with the low-order three bytes of + the MAC address being in the range 00:00:00-3F:FF:FF (to avoid + conflicts with other VMware products). Therefore, even in the case + of manually configured MAC addresses, the IID search space is reduced + from 64 bits to 22 bits. + +4.1.1.2.3. VMware vSphere + + VMware vSphere [vSphere] supports these default MAC address + generation algorithms: + + o Generated addresses + + * Assigned by the vCenter server + + * Assigned by the ESXi host + + o Manually configured addresses + + By default, MAC addresses assigned by the vCenter server use the OUI + 00:50:56 and have the format 00:50:56:XX:YY:ZZ, where XX is + calculated as (0x80 + vCenter Server ID (in the range 0x00-0x3F)), + and XX and YY are random two-digit hexadecimal numbers. Thus, the + possible IID range is 00:50:56:80:00:00-00:50:56:BF:FF:FF; therefore, + the search space for the resulting SLAAC addresses will be 22 bits. + + MAC addresses generated by the ESXi host use the OUI 00:0C:29 and + have the format 00:0C:29:XX:YY:ZZ, where XX, YY, and ZZ are the last + three octets in hexadecimal format of the virtual machine Universally + Unique Identifier (UUID) (based on a hash calculated with the UUID of + the ESXi physical machine and the path to a configuration file). + Thus, the MAC addresses will be in the range + 00:0C:29:00:00:00-00:0C:29:FF:FF:FF; therefore, the search space for + the resulting SLAAC addresses will be 24 bits. + + Finally, manually configured MAC addresses employ the OUI 00:50:56, + with the low-order three bytes being in the range 00:00:00-3F:FF:FF + (to avoid conflicts with other VMware products). Therefore, the + resulting MAC addresses will be in the range + 00:50:56:00:00:00-00:50:56:3F:FF:FF, and the search space for the + corresponding SLAAC addresses will be 22 bits. + + + + + +Gont & Chown Informational [Page 9] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +4.1.1.3. Temporary Addresses + + Privacy concerns [Gont-DEEPSEC2011] [RFC7721] regarding IIDs + embedding IEEE identifiers led to the introduction of "Privacy + Extensions for Stateless Address Autoconfiguration in IPv6" + [RFC4941], also known as "temporary addresses" or "privacy + addresses". Essentially, "temporary addresses" produce random + addresses by concatenating a random identifier to the + autoconfiguration IPv6 prefix advertised in a Router Advertisement + message. + + NOTE: + In addition to their unpredictability, these addresses are + typically short-lived, such that even if an attacker were to learn + of one of these addresses, they would be of use for a limited + period of time. A typical implementation may keep a temporary + address preferred for 24 hours, and configured but deprecated for + seven days. + + It is important to note that "temporary addresses" are generated in + addition to the stable addresses [RFC7721] (such as the traditional + SLAAC addresses based on IEEE identifiers): stable SLAAC addresses + are meant to be employed for "server-like" inbound communications, + while "temporary addresses" are meant to be employed for "client- + like" outbound communications. This means that implementation/use of + "temporary addresses" does not prevent an attacker from leveraging + the predictability of stable SLAAC addresses, since "temporary + addresses" are generated in addition to (rather than as a replacement + of) the stable SLAAC addresses (such as those derived from IEEE + identifiers). + + The benefit that temporary addresses offer in this context is that + they reduce the exposure of the host addresses to any third parties + that may observe traffic sent from a host where temporary addresses + are enabled and used by default. But, in the absence of firewall + protection for the host, its stable SLAAC address remains liable to + be scanned from off-site. + +4.1.1.4. Constant, Semantically Opaque IIDs + + In order to mitigate the security implications arising from the + predictable IPv6 addresses derived from IEEE identifiers, Microsoft + Windows produced an alternative scheme for generating "stable + addresses" (in replacement of the ones embedding IEEE identifiers). + The aforementioned scheme is believed to be an implementation of RFC + 4941 [RFC4941], but without regenerating the addresses over time. + The resulting IIDs are constant across system bootstraps, and also + constant across networks. + + + +Gont & Chown Informational [Page 10] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Assuming no flaws in the aforementioned algorithm, this scheme would + remove any patterns from the SLAAC addresses. + + NOTE: + However, since the resulting IIDs are constant across networks, + these addresses may still be leveraged for host-tracking purposes + [RFC7217] [RFC7721]. + + The benefit of this scheme is thus that the host may be less readily + detected by applying heuristics to an address-scanning attack, but, + in the absence of concurrent use of temporary addresses, the host is + liable to be tracked across visited networks. + +4.1.1.5. Stable, Semantically Opaque IIDs + + In response to the predictability issues discussed in Section 4.1.1.1 + and the privacy issues discussed in [RFC7721], the IETF has + standardized (in [RFC7217]) a method for generating IPv6 IIDs to be + used with IPv6 SLAAC, such that addresses configured using this + method are stable within each subnet, but the IIDs change when hosts + move from one subnet to another. The aforementioned method is meant + to be an alternative to generating IIDs based on IEEE identifiers, + such that the benefits of stable addresses can be achieved without + sacrificing the privacy of users. + + Implementation of this method (in replacement of IIDs based on IEEE + identifiers) eliminates any patterns from the IID, thus benefiting + user privacy and reducing the ease with which addresses can be + scanned. + +4.1.2. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) + + DHCPv6 can be employed as a stateful address configuration mechanism, + in which a server (the DHCPv6 server) leases IPv6 addresses to IPv6 + hosts. As with the IPv4 counterpart, addresses are assigned + according to a configuration-defined address range and policy, with + some DHCPv6 servers assigning addresses sequentially, from a specific + range. In such cases, addresses tend to be predictable. + + NOTE: + For example, if the prefix 2001:db8::/64 is used for assigning + addresses on the local network, the DHCPv6 server might + (sequentially) assign addresses from the range 2001:db8::1 - + 2001:db8::100. + + In most common scenarios, this means that the IID search space will + be reduced from the original 64 bits to 8 or 16 bits. [RFC5157] + recommended that DHCPv6 instead issue addresses randomly from a large + + + +Gont & Chown Informational [Page 11] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + pool; that advice is repeated here. [IIDS-DHCPv6] specifies an + algorithm that can be employed by DHCPv6 servers to produce stable + addresses that do not follow any specific pattern, thus resulting in + an IID search space of 64 bits. + +4.1.3. Manually Configured Addresses + + In some scenarios, node addresses may be manually configured. This + is typically the case for IPv6 addresses assigned to routers (since + routers do not employ automatic address configuration) but also for + servers (since having a stable address that does not depend on the + underlying link-layer address is generally desirable). + + While network administrators are mostly free to select the IID from + any value in the range 1 - 2^64, for the sake of simplicity (i.e., + ease of remembering), they tend to select addresses with one of the + following patterns: + + o low-byte addresses: in which most of the bytes of the IID are set + to 0 (except for the least significant byte) + + o IPv4-based addresses: in which the IID embeds the IPv4 address of + the network interface (as in 2001:db8::192.0.2.1) + + o service port addresses: in which the IID embeds the TCP/UDP + service port of the main service running on that node (as in + 2001:db8::80 or 2001:db8::25) + + o wordy addresses: which encode words (as in 2001:db8::bad:cafe) + + Each of these patterns is discussed in detail in the following + subsections. + +4.1.3.1. Low-Byte Addresses + + The most common form of low-byte addresses is that in which all the + bytes of the IID (except the least significant bytes) are set to zero + (as in 2001:db8::1, 2001:db8::2, etc.). However, it is also common + to find similar addresses in which the two lowest-order 16-bit words + (from the right to left) are set to small numbers (as in + 2001::db8::1:10, 2001:db8::2:10, etc.). Yet it is not uncommon to + find IPv6 addresses in which the second lowest-order 16-bit word + (from right to left) is set to a small value in the range + 0x0000:0x00ff, while the lowest-order 16-bit word (from right to + left) varies in the range 0x0000:0xffff. It should be noted that all + of these address patterns are generally referred to as "low-byte + + + + + +Gont & Chown Informational [Page 12] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + addresses", even when, strictly speaking, it is not only the lowest- + order byte of the IPv6 address that varies from one address to + another. + + In the worst-case scenario, the search space for this pattern is 2^24 + (although most systems can be found by searching 2^16 or even 2^8 + addresses). + +4.1.3.2. IPv4-Based Addresses + + The most common form of these addresses is that in which an IPv4 + address is encoded in the lowest-order 32 bits of the IPv6 address + (usually as a result of the address notation of the form + 2001:db8::192.0.2.1). However, it is also common for administrators + to encode each of the bytes of the IPv4 address in each of the 16-bit + words of the IID (as in, e.g., 2001:db8::192:0:2:1). + + Therefore, the search space for addresses following this pattern is + that of the corresponding IPv4 prefix (or twice the size of that + search space if both forms of "IPv4-based addresses" are to be + searched). + +4.1.3.3. Service-Port Addresses + + Addresses following this pattern include the service port (e.g., 80 + for HTTP) in the lowest-order byte of the IID and have the rest of + the bytes of the IID set to zero. There are a number of variants for + this address pattern: + + o The lowest-order 16-bit word (from right to left) may contain the + service port, and the second lowest-order 16-bit word (from right + to left) may be set to a number in the range 0x0000-0x00ff (as in, + e.g., 2001:db8::1:80). + + o The lowest-order 16-bit word (from right to left) may be set to a + value in the range 0x0000-0x00ff, while the second lowest-order + 16-bit word (from right to left) may contain the service port (as + in, e.g., 2001:db8::80:1). + + o The service port itself might be encoded in decimal or in + hexadecimal notation (e.g., an address embedding the HTTP port + might be 2001:db8::80 or 2001:db8::50) -- with addresses encoding + the service port as a decimal number being more common. + + Considering a maximum of 20 popular service ports, the search space + for addresses following this pattern is, in the worst-case scenario, + 10 * 2^11. + + + + +Gont & Chown Informational [Page 13] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +4.1.3.4. Wordy Addresses + + Since the IPv6 address notation allows for a number of hexadecimal + digits, it is not difficult to encode words into IPv6 addresses (as + in, e.g., 2001:db8::bad:cafe). + + Addresses following this pattern are likely to be explored by means + of "dictionary attacks"; therefore, computing the corresponding + search space is not straightforward. + +4.1.4. IPv6 Addresses Corresponding to Transition/Coexistence + Technologies + + Some transition/coexistence technologies might be leveraged to reduce + the target search space of remote address-scanning attacks, since + they specify how the corresponding IPv6 address must be generated. + For example, in the case of Teredo [RFC4380], the 64-bit IID is + generated from the IPv4 address observed at a Teredo server along + with a UDP port number. + + For obvious reasons, the search space for these addresses will depend + on the specific transition/coexistence technology being employed. + +4.1.5. IPv6 Address Assignment in Real-World Network Scenarios + + Figures 1, 2, and 3 provide a summary of the results obtained by + [Gont-LACSEC2013] when measuring the address patterns employed by web + servers, name servers, and mail servers, respectively. Figure 4 + provides a rough summary of the results obtained by [Malone2008] for + IPv6 routers. Figure 5 provides a summary of the results obtained by + [Ford2013] for clients. + + + + + + + + + + + + + + + + + + + + +Gont & Chown Informational [Page 14] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + +---------------+------------+ + | Address type | Percentage | + +---------------+------------+ + | IEEE-based | 1.44% | + +---------------+------------+ + | Embedded-IPv4 | 25.41% | + +---------------+------------+ + | Embedded-Port | 3.06% | + +---------------+------------+ + | ISATAP | 0.00% | + +---------------+------------+ + | Low-byte | 56.88% | + +---------------+------------+ + | Byte-pattern | 6.97% | + +---------------+------------+ + | Randomized | 6.24% | + +---------------+------------+ + + Figure 1: Measured Web Server Addresses + + +---------------+------------+ + | Address type | Percentage | + +---------------+------------+ + | IEEE-based | 0.67% | + +---------------+------------+ + | Embedded-IPv4 | 22.11% | + +---------------+------------+ + | Embedded-Port | 6.48% | + +---------------+------------+ + | ISATAP | 0.00% | + +---------------+------------+ + | Low-byte | 56.58% | + +---------------+------------+ + | Byte-pattern | 11.07% | + +---------------+------------+ + | Randomized | 3.09% | + +---------------+------------+ + + Figure 2: Measured Name Server Addresses + + + + + + + + + + + + +Gont & Chown Informational [Page 15] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + +---------------+------------+ + | Address type | Percentage | + +---------------+------------+ + | IEEE-based | 0.48% | + +---------------+------------+ + | Embedded-IPv4 | 4.02% | + +---------------+------------+ + | Embedded-Port | 1.07% | + +---------------+------------+ + | ISATAP | 0.00% | + +---------------+------------+ + | Low-byte | 92.65% | + +---------------+------------+ + | Byte-pattern | 1.20% | + +---------------+------------+ + | Randomized | 0.59% | + +---------------+------------+ + + Figure 3: Measured Mail Server Addresses + + +--------------+------------+ + | Address type | Percentage | + +--------------+------------+ + | Low-byte | 70.00% | + +--------------+------------+ + | IPv4-based | 5.00% | + +--------------+------------+ + | SLAAC | 1.00% | + +--------------+------------+ + | Wordy | <1.00% | + +--------------+------------+ + | Randomized | <1.00% | + +--------------+------------+ + | Teredo | <1.00% | + +--------------+------------+ + | Other | <1.00% | + +--------------+------------+ + + Figure 4: Measured Router Addresses + + + + + + + + + + + + +Gont & Chown Informational [Page 16] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + +---------------+------------+ + | Address type | Percentage | + +---------------+------------+ + | IEEE-based | 7.72% | + +---------------+------------+ + | Embedded-IPv4 | 14.31% | + +---------------+------------+ + | Embedded-Port | 0.21% | + +---------------+------------+ + | ISATAP | 1.06% | + +---------------+------------+ + | Randomized | 69.73% | + +---------------+------------+ + | Low-byte | 6.23% | + +---------------+------------+ + | Byte-pattern | 0.74% | + +---------------+------------+ + + Figure 5: Measured Client Addresses + + NOTE: + "ISATAP" stands for "Intra-Site Automatic Tunnel Addressing + Protocol" [RFC5214]. + + It should be clear from these measurements that a very high + percentage of host and router addresses follow very specific + patterns. + + Figure 5 shows that while around 70% of clients observed in this + measurement appear to be using temporary addresses, a significant + number of clients still expose IEEE-based addresses and addresses + using embedded IPv4 (thus also revealing IPv4 addresses). Besides, + as noted in Section 4.1.1.3, temporary addresses are employed along + with stable IPv6 addresses; thus, hosts employing a temporary address + may still be the subject of address-scanning attacks that target + their stable address(es). + + [ADDR-ANALYSIS] contains a spatial and temporal analysis of IPv6 + addresses corresponding to clients and routers. + +4.2. IPv6 Address Scanning of Remote Networks + + Although attackers have been able to get away with "brute-force" + address-scanning attacks in IPv4 networks (thanks to the lesser + search space), successfully performing a brute-force address-scanning + attack of an entire /64 network would be infeasible. As a result, it + is expected that attackers will leverage the IPv6 address patterns + discussed in Section 4.1 to reduce the IPv6 address search space. + + + +Gont & Chown Informational [Page 17] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + IPv6 address scanning of remote networks should consider an + additional factor not present for the IPv4 case: since the typical + IPv6 subnet is a /64, scanning an entire /64 could, in theory, lead + to the creation of 2^64 entries in the Neighbor Cache of the last-hop + router. Unfortunately, a number of IPv6 implementations have been + found to be unable to properly handle a large number of entries in + the Neighbor Cache; hence, these address-scanning attacks may have + the side effect of resulting in a Denial-of-Service (DoS) attack + [CPNI-IPv6] [RFC6583]. + + [RFC7421] discusses the "default" /64 boundary for host subnets and + the assumptions surrounding it. While there are reports of sites + implementing IPv6 subnets of size /112 or smaller to reduce concerns + about the above attack, such smaller subnets are likely to make + address-scanning attacks more feasible, in addition to encountering + the issues with non-/64 host subnets discussed in [RFC7421]. + +4.2.1. Reducing the Subnet ID Search Space + + When address scanning a remote network, consideration is required to + select which subnet IDs to choose. A typical site might have a /48 + allocation, which would mean up to 65,000 or so IPv6 /64 subnets to + be scanned. + + However, in the same way the search space for the IID can be reduced, + we may also be able to reduce the subnet ID search space in a number + of ways, by guessing likely address plan schemes or using any + complementary clues that might exist from other sources or + observations. For example, there are a number of documents available + online (e.g., [RFC5375]) that provide recommendations for the + allocation of address space, which address various operational + considerations, including Regional Internet Registry (RIR) assignment + policy, ability to delegate reverse DNS zones to different servers, + ability to aggregate routes efficiently, address space preservation, + ability to delegate address assignment within the organization, + ability to add/allocate new sites/prefixes to existing entities + without updating Access Control Lists (ACLs), and ability to + de-aggregate and advertise subspaces via various Autonomous System + (AS) interfaces. + + Address plans might include use of subnets that: + + o Run from low ID upwards, e.g., 2001:db8:0::/64, 2001:db8:1::/64, + etc. + + o Use building numbers, in hexadecimal or decimal form. + + o Use Virtual Local Area Network (VLAN) numbers. + + + +Gont & Chown Informational [Page 18] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + o Use an IPv4 subnet number in a dual-stack target, e.g., a site + with a /16 for IPv4 might use /24 subnets, and the IPv6 address + plan may reuse the third byte of the IPv4 address as the IPv6 + subnet ID. + + o Use the service "color", as defined for service-based prefix + coloring, or semantic prefixes. For example, a site using a + specific coloring for a specific service such as Voice over IP + (VoIP) may reduce the subnet ID search space for those devices. + + The net effect is that the address space of an organization may be + highly structured, and allocations of individual elements within this + structure may be predictable once other elements are known. + + In general, any subnet ID address plan may convey information, or be + based on known information, which may in turn be of advantage to an + attacker. + +4.3. IPv6 Address Scanning of Local Networks + + IPv6 address scanning in Local Area Networks (LANs) could be + considered, to some extent, a completely different problem than that + of scanning a remote IPv6 network. The main difference is that use + of link-local multicast addresses can relieve the attacker of + searching for unicast addresses in a large IPv6 address space. + + NOTE: + While a number of other network reconnaissance vectors (such as + network snooping, leveraging Neighbor Discovery traffic, etc.) are + available when scanning a local network, this section focuses only + on address-scanning attacks (a la "ping sweep"). + + An attacker can simply send probe packets to the all-nodes link-local + multicast address (ff02::1), such that responses are elicited from + all local nodes. + + Since Windows systems (Vista, 7, etc.) do not respond to ICMPv6 Echo + Request messages sent to multicast addresses, IPv6 address-scanning + tools typically employ a number of additional probe packets to elicit + responses from all the local nodes. For example, unrecognized IPv6 + options of type 10xxxxxx elicit Internet Control Message Protocol + version 6 (ICMPv6) Parameter Problem, code 2, error messages. + + Many address-scanning tools discover only IPv6 link-local addresses + (rather than, e.g., the global addresses of the target systems): + since the probe packets are typically sent with the attacker's IPv6 + link-local address, the "victim" nodes send the response packets + using the IPv6 link-local address of the corresponding network + + + +Gont & Chown Informational [Page 19] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + interface (as specified by the IPv6 address-selection rules + [RFC6724]). However, sending multiple probe packets, with each + packet employing source addresses from different prefixes, typically + helps to overcome this limitation. + +4.4. Existing IPv6 Address-Scanning Tools + +4.4.1. Remote IPv6 Network Address Scanners + + IPv4 address-scanning tools have traditionally carried out their task + by probing an entire address range (usually the entire address range + comprised by the target subnetwork). One might argue that the reason + for which they have been able to get away with such somewhat + "rudimentary" techniques is that the scale or challenge of the task + is so small in the IPv4 world that a "brute-force" attack is "good + enough". However, the scale of the "address-scanning" task is so + large in IPv6 that attackers must be very creative to be "good + enough". Simply sweeping an entire /64 IPv6 subnet would just not be + feasible. + + Many address-scanning tools do not even support sweeping an IPv6 + address range. On the other hand, the alive6 tool from [THC-IPV6] + supports sweeping address ranges, thus being able to leverage some + patterns found in IPv6 addresses, such as the incremental addresses + resulting from some DHCPv6 setups. Finally, the scan6 tool from + [IPv6-Toolkit] supports sweeping address ranges and can also leverage + all the address patterns described in Section 4.1 of this document. + + Clearly, a limitation of many of the currently available tools for + IPv6 address scanning is that they lack an appropriately tuned + "heuristics engine" that can help reduce the search space, such that + the problem of IPv6 address scanning becomes tractable. + + It should be noted that IPv6 network monitoring and management tools + also need to build and maintain information about the hosts in their + network. Such systems can no longer scan internal systems in a + reasonable time to build a database of connected systems. Rather, + such systems will need more efficient approaches, e.g., by polling + network devices for data held about observed IP addresses, MAC + addresses, physical ports used, etc. Such an approach can also + enhance address accountability, by mapping IPv4 and IPv6 addresses to + observed MAC addresses. This of course implies that any access + control mechanisms for querying such network devices, e.g., community + strings for SNMP, should be set appropriately to avoid an attacker + being able to gather address information remotely. + + + + + + +Gont & Chown Informational [Page 20] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +4.4.2. Local IPv6 Network Address Scanners + + There are a variety of publicly available local IPv6 network address- + scanners: + + o Current versions of nmap [nmap2015] implement this functionality. + + o The Hacker's Choice (THC) IPv6 Attack Toolkit [THC-IPV6] includes + a tool (alive6) that implements this functionality. + + o SI6 Network's IPv6 Toolkit [IPv6-Toolkit] includes a tool (scan6) + that implements this functionality. + +4.5. Mitigations + + IPv6 address-scanning attacks can be mitigated in a number of ways. + A non-exhaustive list of the possible mitigations includes: + + o Employing [RFC7217] (stable, semantically opaque IIDs) in + replacement of addresses based on IEEE identifiers, such that any + address patterns are eliminated. + + o Employing Intrusion Prevention Systems (IPSs) at the perimeter. + + o Enforcing IPv6 packet filtering where applicable (see, e.g., + [RFC4890]). + + o Employing manually configured MAC addresses if virtual machines + are employed and "resistance" to address-scanning attacks is + deemed desirable, such that even if the virtual machines employ + IEEE-derived IIDs, they are generated from non-predictable MAC + addresses. + + o Avoiding use of sequential addresses when using DHCPv6. Ideally, + the DHCPv6 server would allocate random addresses from a large + pool (see, e.g., [IIDS-DHCPv6]). + + o Using the "default" /64 size IPv6 subnet prefixes. + + o In general, avoiding being predictable in the way addresses are + assigned. + + It should be noted that some of the aforementioned mitigations are + operational, while others depend on the availability of specific + protocol features (such as [RFC7217]) on the corresponding nodes. + + + + + + +Gont & Chown Informational [Page 21] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Additionally, while some resistance to address-scanning attacks is + generally desirable (particularly when lightweight mitigations are + available), there are scenarios in which mitigation of some address- + scanning vectors is unlikely to be a high priority (if at all + possible). And one should always remember that security by obscurity + is not a reasonable defense in itself; it may only be one (relatively + small) layer in a broader security environment. + + Two of the techniques discussed in this document for local address- + scanning attacks are those that employ multicasted ICMPv6 Echo + Requests and multicasted IPv6 packets containing unsupported options + of type 10xxxxxx. These two vectors could be easily mitigated by + configuring nodes to not respond to multicasted ICMPv6 Echo Requests + (default on Windows systems) and by updating the IPv6 specifications + (and/or possibly configuring local nodes) such that multicasted + packets never elicit ICMPv6 error messages (even if they contain + unsupported options of type 10xxxxxx). + + NOTE: + [SMURF-AMPLIFIER] proposed such an update to the IPv6 + specifications. + + In any case, when it comes to local networks, there are a variety of + network reconnaissance vectors. Therefore, even if address-scanning + vectors were mitigated, an attacker could still rely on, e.g., + protocols employed for the so-called "service discovery protocols" + (see Section 5.2) or eventually rely on network snooping as a last + resort for network reconnaissance. There is ongoing work in the IETF + on extending mDNS, or at least DNS-based service discovery, to work + across a whole site, rather than in just a single subnet, which will + have associated security implications. + +4.6. Conclusions + + In the previous subsections, we have shown why a /64 host subnet may + be more vulnerable to address-based scanning than might intuitively + be thought and how an attacker might reduce the target search space + when performing an address-scanning attack. + + We have described a number of mitigations against address-scanning + attacks, including the replacement of traditional SLAAC with stable + semantically opaque IIDs (which requires support from system + vendors). We have also offered some practical guidance in regard to + the principle of avoiding predictability in host addressing schemes. + Finally, examples of address-scanning approaches and tools are + discussed in the appendices. + + + + + +Gont & Chown Informational [Page 22] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + While most early IPv6-enabled networks remain dual stack, they are + more likely to be scanned and attacked over IPv4 transport, and one + may argue that the IPv6-specific considerations discussed here are + not of an immediate concern. However, an early IPv6 deployment + within a dual-stack network may be seen by an attacker as a + potentially "easier" target if the implementation of security + policies is not as strict for IPv6 (for whatever reason). As + IPv6-only networks become more common, the above considerations will + be of much greater importance. + +5. Alternative Methods to Glean IPv6 Addresses + + The following subsections describe alternative methods by which an + attacker might attempt to glean IPv6 addresses for subsequent + probing. + +5.1. Leveraging the Domain Name System (DNS) for Network Reconnaissance + +5.1.1. DNS Advertised Hosts + + Any systems that are "published" in the DNS, e.g., Mail Exchange (MX) + relays or web servers, will remain open to probing from the very fact + that their IPv6 addresses are publicly available. It is worth noting + that where the addresses used at a site follow specific patterns, + publishing just one address may lead to an attack upon the other + nodes. + + Additionally, we note that publication of IPv6 addresses in the DNS + should not discourage the elimination of IPv6 address patterns: if + any address patterns are eliminated from addresses published in the + DNS, an attacker may have to rely on performing dictionary-based DNS + lookups in order to find all systems in a target network (which is + generally less reliable and more time/traffic consuming than mapping + nodes with predictable IPv6 addresses). + +5.1.2. DNS Zone Transfers + + A DNS zone transfer (DNS query type "AXFR") [RFC1034] [RFC1035] can + readily provide information about potential attack targets. + Restricting zone transfers is thus probably more important for IPv6, + even if it is already good practice to restrict them in the IPv4 + world. + +5.1.3. DNS Brute Forcing + + Attackers may employ DNS brute-forcing techniques by testing for the + presence of DNS AAAA records against commonly used host names. + + + + +Gont & Chown Informational [Page 23] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +5.1.4. DNS Reverse Mappings + + [van-Dijk] describes an interesting technique that employs DNS + reverse mappings for network reconnaissance. Essentially, the + attacker walks through the "ip6.arpa" zone looking up PTR records, in + the hopes of learning the IPv6 addresses of hosts in a given target + network (assuming that the reverse mappings have been configured, of + course). What is most interesting about this technique is that it + can greatly reduce the IPv6 address search space. + + Basically, an attacker would walk the ip6.arpa zone corresponding to + a target network (e.g., "0.8.0.0.8.b.d.0.1.0.0.2.ip6.arpa." for + "2001:db8:80::/48"), issuing queries for PTR records corresponding to + the domain names "0.0.8.0.0.8.b.d.0.1.0.0.2.ip6.arpa.", + "1.0.8.0.0.8.b.d.0.1.0.0.2.ip6.arpa.", etc. If, say, there were PTR + records for any hosts "starting" with the domain name + "0.0.8.0.0.8.b.d.0.1.0.0.2.ip6.arpa." (e.g., the ip6.arpa domain name + corresponding to the IPv6 address 2001:db8:80::1), the response would + contain an RCODE of 0 (no error). Otherwise, the response would + contain an RCODE of 4 (NXDOMAIN). As noted in [van-Dijk], this + technique allows for a tremendous reduction in the "IPv6 address" + search space. + + NOTE: + Some name servers, incorrectly implementing the DNS protocol, + reply NXDOMAIN instead of NODATA (NOERROR=0 and ANSWER=0) when + encountering a domain without any resource records but that has + child domains, something that is very common in ip6.arpa (these + domains are called ENT for Empty Non-Terminals; see [RFC7719]). + When scanning ip6.arpa, this behavior may slow down or completely + prevent the exploration of ip6.arpa. Nevertheless, since such + behavior is wrong (see [NXDOMAIN-DEF]), one cannot rely on it to + "secure" ip6.arpa against tree walking. + + [IPv6-RDNS] analyzes different approaches and considerations for + ISPs in managing the ip6.arpa zone for IPv6 address space assigned + to many customers, which may affect the technique described in + this section. + +5.2. Leveraging Local Name Resolution and Service Discovery Services + + A number of protocols allow for unmanaged local name resolution and + service. For example, mDNS [RFC6762] and DNS Service Discovery (DNS- + SD) [RFC6763], or Link-Local Multicast Name Resolution (LLMNR) + [RFC4795], are examples of such protocols. + + + + + + +Gont & Chown Informational [Page 24] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + NOTE: + Besides the Graphical User Interfaces (GUIs) included in products + supporting such protocols, command-line tools such as mdns-scan + [mdns-scan] and mzclient [mzclient] can help discover IPv6 hosts + employing mDNS/DNS-SD. + +5.3. Public Archives + + Public mailing-list archives or Usenet news messages archives may + prove to be a useful channel for an attacker, since hostnames and/or + IPv6 addresses could be easily obtained by inspection of the (many) + "Received from:" or other header lines in the archived email or + Usenet news messages. + +5.4. Application Participation + + Peer-to-peer applications often include some centralized server that + coordinates the transfer of data between peers. For example, + BitTorrent [BitTorrent] builds swarms of nodes that exchange chunks + of files, with a tracker passing information about peers with + available chunks of data between the peers. Such applications may + offer an attacker a source of peer addresses to probe. + +5.5. Inspection of the IPv6 Neighbor Cache and Routing Table + + Information about other systems connected to the local network might + be readily available from the Neighbor Cache [RFC4861] and/or the + routing table of any system connected to such network. Source + Address Validation Improvement (SAVI) [RFC6620] also builds a cache + of IPv6 and link-layer addresses (without actively participating in + the Neighbor Discovery packet exchange) and hence is another source + of similar information. + + These data structures could be inspected via either "login" access or + SNMP. While this requirement may limit the applicability of this + technique, there are a number of scenarios in which this technique + might be of use. For example, security audit tools might be provided + with the necessary credentials such that the Neighbor Cache and the + routing table of all systems for which the tool has "login" or SNMP + access can be automatically gleaned. On the other hand, IPv6 worms + [V6-WORMS] could leverage this technique for the purpose of spreading + on the local network, since they will typically have access to the + Neighbor Cache and routing table of an infected system. + + Section 2.5.1.4 of [OPSEC-IPv6] discusses additional considerations + for the inspection of the IPv6 Neighbor Cache. + + + + + +Gont & Chown Informational [Page 25] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +5.6. Inspection of System Configuration and Log Files + + Nodes are generally configured with the addresses of other important + local computers, such as email servers, local file servers, web proxy + servers, recursive DNS servers, etc. The /etc/hosts file in UNIX- + like systems, Secure Shell (SSH) known_hosts files, or the Microsoft + Windows registry are just some examples of places where interesting + information about such systems might be found. + + Additionally, system log files (including web server logs, etc.) may + also prove to be a useful source for an attacker. + + While the required credentials to access the aforementioned + configuration and log files may limit the applicability of this + technique, there are a number of scenarios in which this technique + might be of use. For example, security audit tools might be provided + with the necessary credentials such that these files can be + automatically accessed. On the other hand, IPv6 worms could leverage + this technique for the purpose of spreading on the local network, + since they will typically have access to these files on an infected + system [V6-WORMS]. + +5.7. Gleaning Information from Routing Protocols + + Some organizational IPv6 networks employ routing protocols to + dynamically maintain routing information. In such an environment, a + local attacker could become a passive listener of the routing + protocol, to determine other valid subnets/prefixes and some router + addresses within that organization [V6-WORMS]. + +5.8. Gleaning Information from IP Flow Information Export (IPFIX) + + IPFIX [RFC7012] can aggregate the flows by source addresses and hence + may be leveraged for obtaining a list of "active" IPv6 addresses. + Additional discussion of IPFIX can be found in Section 2.5.1.2 of + [OPSEC-IPv6]. + +5.9. Obtaining Network Information with traceroute6 + + IPv6 traceroute [traceroute6] and similar tools (such as path6 from + [IPv6-Toolkit]) can be employed to find router addresses and valid + network prefixes. + + + + + + + + + +Gont & Chown Informational [Page 26] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +5.10. Gleaning Information from Network Devices Using SNMP + + SNMP can be leveraged to obtain information from a number of data + structures such as the Neighbor Cache [RFC4861], the routing table, + and the SAVI [RFC6620] cache of IPv6 and link-layer addresses. SNMP + access should be secured, such that unauthorized access to the + aforementioned information is prevented. + +5.11. Obtaining Network Information via Traffic Snooping + + Snooping network traffic can help in discovering active nodes in a + number of ways. Firstly, each captured packet will reveal the source + and destination of the packet. Secondly, the captured traffic may + correspond to network protocols that transfer information such as + host or router addresses, network topology information, etc. + +6. Conclusions + + This document explores the topic of network reconnaissance in IPv6 + networks. It analyzes the feasibility of address-scanning attacks in + IPv6 networks and shows that the search space for such attacks is + typically much smaller than the one traditionally assumed (64 bits). + + Additionally, this document explores a plethora of other network + reconnaissance techniques, ranging from inspecting the IPv6 Network + Cache of an attacker-controlled system to gleaning information about + IPv6 addresses from public mailing-list archives or Peer-to-Peer + (P2P) protocols. + + We expect traditional address-scanning attacks to become more and + more elaborated (i.e., less "brute force"), and other network + reconnaissance techniques to be actively explored, as global + deployment of IPv6 increases and, more specifically, as more + IPv6-only devices are deployed. + +7. Security Considerations + + This document reviews methods by which addresses of hosts within IPv6 + subnets can be determined. As such, it raises no new security + concerns. + + + + + + + + + + + +Gont & Chown Informational [Page 27] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +8. References + +8.1. Normative References + + [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", + STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, + <http://www.rfc-editor.org/info/rfc1034>. + + [RFC1035] Mockapetris, P., "Domain names - implementation and + specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, + November 1987, <http://www.rfc-editor.org/info/rfc1035>. + + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, + December 1998, <http://www.rfc-editor.org/info/rfc2460>. + + [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, + C., and M. Carney, "Dynamic Host Configuration Protocol + for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July + 2003, <http://www.rfc-editor.org/info/rfc3315>. + + [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through + Network Address Translations (NATs)", RFC 4380, + DOI 10.17487/RFC4380, February 2006, + <http://www.rfc-editor.org/info/rfc4380>. + + [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, + "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, + DOI 10.17487/RFC4861, September 2007, + <http://www.rfc-editor.org/info/rfc4861>. + + [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless + Address Autoconfiguration", RFC 4862, + DOI 10.17487/RFC4862, September 2007, + <http://www.rfc-editor.org/info/rfc4862>. + + [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy + Extensions for Stateless Address Autoconfiguration in + IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, + <http://www.rfc-editor.org/info/rfc4941>. + + [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site + Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, + DOI 10.17487/RFC5214, March 2008, + <http://www.rfc-editor.org/info/rfc5214>. + + + + + + +Gont & Chown Informational [Page 28] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + [RFC6620] Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS + SAVI: First-Come, First-Served Source Address Validation + Improvement for Locally Assigned IPv6 Addresses", + RFC 6620, DOI 10.17487/RFC6620, May 2012, + <http://www.rfc-editor.org/info/rfc6620>. + + [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, + "Default Address Selection for Internet Protocol Version 6 + (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, + <http://www.rfc-editor.org/info/rfc6724>. + + [RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model + for IP Flow Information Export (IPFIX)", RFC 7012, + DOI 10.17487/RFC7012, September 2013, + <http://www.rfc-editor.org/info/rfc7012>. + + [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 + Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, + February 2014, <http://www.rfc-editor.org/info/rfc7136>. + + [RFC7217] Gont, F., "A Method for Generating Semantically Opaque + Interface Identifiers with IPv6 Stateless Address + Autoconfiguration (SLAAC)", RFC 7217, + DOI 10.17487/RFC7217, April 2014, + <http://www.rfc-editor.org/info/rfc7217>. + +8.2. Informative References + + [ADDR-ANALYSIS] + Plonka, D. and A. Berger, "Temporal and Spatial + Classification of Active IPv6 Addresses", ACM Internet + Measurement Conference (IMC), Tokyo, Japan, Pages 509-522, + DOI 10.1145/2815675.2815678, October 2015, + <http://conferences2.sigcomm.org/imc/2015/papers/ + p509.pdf>. + + [BitTorrent] + Wikipedia, "BitTorrent", November 2015, + <https://en.wikipedia.org/w/ + index.php?title=BitTorrent&oldid=690381343>. + + [CPNI-IPv6] + Gont, F., "Security Assessment of the Internet Protocol + version 6 (IPv6)", UK Centre for the Protection of + National Infrastructure, (available on request). + + + + + + +Gont & Chown Informational [Page 29] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + [DEFAULT-IIDS] + Gont, F., Cooper, A., Thaler, D., and W. Liu, + "Recommendation on Stable IPv6 Interface Identifiers", + Work in Progress, draft-ietf-6man-default-iids-10, + February 2016. + + [Ford2013] Ford, M., "IPv6 Address Analysis - Privacy In, Transition + Out", May 2013, + <http://www.internetsociety.org/blog/2013/05/ + ipv6-address-analysis-privacy-transition-out>. + + [Gont-DEEPSEC2011] + Gont, F., "Results of a Security Assessment of the + Internet Protocol version 6 (IPv6)", DEEPSEC + Conference, Vienna, Austria, November 2011, + <http://www.si6networks.com/presentations/deepsec2011/ + fgont-deepsec2011-ipv6-security.pdf>. + + [Gont-LACSEC2013] + Gont, F., "IPv6 Network Reconnaissance: Theory & + Practice", LACSEC Conference, Medellin, Colombia, May + 2013, <http://www.si6networks.com/presentations/lacnic19/ + lacsec2013-fgont-ipv6-network-reconnaissance.pdf>. + + [IIDS-DHCPv6] + Gont, F. and W. Liu, "A Method for Generating Semantically + Opaque Interface Identifiers with Dynamic Host + Configuration Protocol for IPv6 (DHCPv6)", Work in + Progress, draft-ietf-dhc-stable-privacy-addresses-02, + April 2015. + + [IPV6-EXT-HEADERS] + Gont, F., Linkova, J., Chown, T., and W. Liu, + "Observations on the Dropping of Packets with IPv6 + Extension Headers in the Real World", Work in Progress, + draft-ietf-v6ops-ipv6-ehs-in-real-world-02, December 2015. + + [IPv6-RDNS] + Howard, L., "Reverse DNS in IPv6 for Internet Service + Providers", Work in Progress, draft-ietf-dnsop-isp- + ip6rdns-00, October 2015. + + [IPv6-Toolkit] + SI6 Networks, "SI6 Networks' IPv6 Toolkit", + <http://www.si6networks.com/tools/ipv6toolkit>. + + + + + + +Gont & Chown Informational [Page 30] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + [Malone2008] + Malone, D., "Observations of IPv6 Addresses", Passive and + Active Network Measurement (PAM 2008, LNCS 4979), + DOI 10.1007/978-3-540-79232-1_3, April 2008, + <http://www.maths.tcd.ie/~dwmalone/p/addr-pam08.pdf>. + + [mdns-scan] + Poettering, L., "mdns-scan(1) Manual Page", + <http://manpages.ubuntu.com/manpages/precise/man1/ + mdns-scan.1.html>. + + [mzclient] Bockover, A., "Mono Zeroconf Project -- mzclient command- + line tool", + <http://www.mono-project.com/archived/monozeroconf/>. + + [nmap2015] Lyon, Gordon "Fyodor", "Nmap 7.00", November 2015, + <http://insecure.org>. + + [NXDOMAIN-DEF] + Bortzmeyer, S. and S. Huque, "NXDOMAIN really means there + is nothing underneath", Work in Progress, draft-ietf- + dnsop-nxdomain-cut-00, December 2015. + + [OPSEC-IPv6] + Chittimaneni, K., Kaeo, M., and E. Vyncke, "Operational + Security Considerations for IPv6 Networks", Work in + Progress, draft-ietf-opsec-v6-07, September 2015. + + [RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local + Multicast Name Resolution (LLMNR)", RFC 4795, + DOI 10.17487/RFC4795, January 2007, + <http://www.rfc-editor.org/info/rfc4795>. + + [RFC4890] Davies, E. and J. Mohacsi, "Recommendations for Filtering + ICMPv6 Messages in Firewalls", RFC 4890, + DOI 10.17487/RFC4890, May 2007, + <http://www.rfc-editor.org/info/rfc4890>. + + [RFC5157] Chown, T., "IPv6 Implications for Network Scanning", + RFC 5157, DOI 10.17487/RFC5157, March 2008, + <http://www.rfc-editor.org/info/rfc5157>. + + [RFC5375] Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O., + and C. Hahn, "IPv6 Unicast Address Assignment + Considerations", RFC 5375, DOI 10.17487/RFC5375, December + 2008, <http://www.rfc-editor.org/info/rfc5375>. + + + + + +Gont & Chown Informational [Page 31] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + [RFC6583] Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational + Neighbor Discovery Problems", RFC 6583, + DOI 10.17487/RFC6583, March 2012, + <http://www.rfc-editor.org/info/rfc6583>. + + [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, + DOI 10.17487/RFC6762, February 2013, + <http://www.rfc-editor.org/info/rfc6762>. + + [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service + Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, + <http://www.rfc-editor.org/info/rfc6763>. + + [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., + Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit + Boundary in IPv6 Addressing", RFC 7421, + DOI 10.17487/RFC7421, January 2015, + <http://www.rfc-editor.org/info/rfc7421>. + + [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS + Terminology", RFC 7719, DOI 10.17487/RFC7719, December + 2015, <http://www.rfc-editor.org/info/rfc7719>. + + [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy + Considerations for IPv6 Address Generation Mechanisms", + RFC 7721, DOI 10.17487/RFC7721, March 2016, + <http://www.rfc-editor.org/info/rfc7721>. + + [SMURF-AMPLIFIER] + Gont, F. and W. Liu, "Security Implications of IPv6 + Options of Type 10xxxxxx", Work in Progress, draft-gont- + 6man-ipv6-smurf-amplifier-03, March 2013. + + [THC-IPV6] "THC-IPV6", <http://www.thc.org/thc-ipv6/>. + + [traceroute6] + FreeBSD, "FreeBSD System Manager's Manual: traceroute6(8) + manual page", August 2009, <https://www.freebsd.org/cgi/ + man.cgi?query=traceroute6>. + + [V6-WORMS] Bellovin, S., Cheswick, B., and A. Keromytis, "Worm + propagation strategies in an IPv6 Internet", Vol. 31, No. + 1, pp. 70-76, February 2006, + <https://www.cs.columbia.edu/~smb/papers/v6worms.pdf>. + + [van-Dijk] van Dijk, P., "Finding v6 hosts by efficiently mapping + ip6.arpa", March 2012, <http://7bits.nl/blog/2012/03/26/ + finding-v6-hosts-by-efficiently-mapping-ip6-arpa>. + + + +Gont & Chown Informational [Page 32] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + [VBox2011] VirtualBox, "Oracle VM VirtualBox User Manual", + Version 4.1.2, August 2011, <http://www.virtualbox.org>. + + [vmesx2011] + VMware, "Setting a static MAC address for a virtual NIC + (219)", VMware Knowledge Base, August 2011, + <http://kb.vmware.com/selfservice/microsites/ + search.do?language=en_US&cmd=displayKC&externalId=219>. + + [vSphere] VMware, "vSphere Networking", vSphere 5.5, Update 2, + September 2014, <http://pubs.vmware.com/ + vsphere-55/topic/com.vmware.ICbase/PDF/ + vsphere-esxi-vcenter-server-552-networking-guide.pdf>. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Gont & Chown Informational [Page 33] + +RFC 7707 IPv6 Reconnaissance March 2016 + + +Appendix A. Implementation of a Full-Fledged IPv6 Address-Scanning Tool + + This section describes the implementation of a full-fledged IPv6 + address-scanning tool. Appendix A.1 discusses the selection of host + probes. Appendix A.2 describes the implementation of an IPv6 address + scanner for local area networks. Appendix A.3 outlines the + implementation of a general (i.e., non-local) IPv6 address scanner. + +A.1. Host-Probing Considerations + + A number of factors should be considered when selecting the probe + packet types and the probing rate for an IPv6 address-scanning tool. + + Firstly, some hosts (or border firewalls) might be configured to + block or rate limit some specific packet types. For example, it is + usual for host and router implementations to rate-limit ICMPv6 error + traffic. Additionally, some firewalls might be configured to block + or rate limit incoming ICMPv6 echo request packets (see, e.g., + [RFC4890]). + + NOTE: + As noted earlier in this document, Windows systems simply do not + respond to ICMPv6 echo requests sent to multicast IPv6 addresses. + + Among the possible probe types are: + + o ICMPv6 Echo Request packets (meant to elicit ICMPv6 Echo Replies), + + o TCP SYN segments (meant to elicit SYN/ACK or RST segments), + + o TCP segments that do not contain the ACK bit set (meant to elicit + RST segments), + + o UDP datagrams (meant to elicit a UDP application response or an + ICMPv6 Port Unreachable), + + o IPv6 packets containing any suitable payload and an unrecognized + extension header (meant to elicit ICMPv6 Parameter Problem error + messages), or + + o IPv6 packets containing any suitable payload and an unrecognized + option of type 10xxxxxx (meant to elicit an ICMPv6 Parameter + Problem error message). + + Selecting an appropriate probe packet might help conceal the ongoing + attack, but it may also be actually necessary if host or network + configuration causes certain probe packets to be dropped. + + + + +Gont & Chown Informational [Page 34] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Some address-scanning tools (such as scan6 of [IPv6-Toolkit]) + incorporate support for IPv6 extension headers. In some cases, + inserting some IPv6 extension headers in the probe packet may allow + some filtering policies or monitoring devices to be circumvented. + However, it may also result in the probe packets being dropped, as a + result of the widespread dropping of IPv6 packets that employ IPv6 + extension headers (see [IPV6-EXT-HEADERS]). + + Another factor to consider is the address-probing rate. Clearly, the + higher the rate, the smaller the amount of time required to perform + the attack. However, the probing rate should not be too high, or + else: + + 1. the attack might cause network congestion, thus resulting in + packet loss. + + 2. the attack might hit rate limiting, thus resulting in packet + loss. + + 3. the attack might reveal underlying problems in Neighbor Discovery + implementations, thus leading to packet loss and possibly even + Denial of Service. + + Packet loss is undesirable, since it would mean that an "alive" node + might remain undetected as a result of a lost probe or response. + Such losses could be the result of congestion (in case the attacker + is scanning a target network at a rate higher than the target network + can handle) or may be the result of rate limiting (as it would be + typically the case if ICMPv6 is employed for the probe packets). + Finally, as discussed in [CPNI-IPv6] and [RFC6583], some IPv6 router + implementations have been found to be unable to perform decent + resource management when faced with Neighbor Discovery traffic + involving a large number of local nodes. This essentially means that + regardless of the type of probe packets, an address-scanning attack + might result in a DoS of the target network, with the same (or worse) + effects as that of network congestion or rate limiting. + + The specific rates at which each of these issues may come into play + vary from one scenario to another and depend on the type of deployed + routers/firewalls, configuration parameters, etc. + +A.2. Implementation of an IPv6 Local Address-Scanning Tool + + scan6 [IPv6-Toolkit] is a full-fledged IPv6 local address-scanning + tool, which has proven to be effective and efficient for the + discovery of IPv6 hosts on a local network. + + + + + +Gont & Chown Informational [Page 35] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + The scan6 tool operates (roughly) as follows: + + 1. The tool learns the local prefixes used for autoconfiguration and + generates/configures one address for each local prefix (in + addition to a link-local address). + + 2. An ICMPv6 Echo Request message destined to the all-nodes on-link + multicast address (ff02::1) is sent from each of the addresses + "configured" in the previous step. Because of the different + source addresses, each probe packet causes the victim nodes to + use different source addresses for the response packets (this + allows the tool to learn virtually all the addresses in use in + the local network segment). + + 3. The same procedure of the previous bullet is performed, but this + time with ICMPv6 packets that contain an unrecognized option of + type 10xxxxxx, such that ICMPv6 Parameter Problem error messages + are elicited. This allows the tool to discover, e.g., Windows + nodes, which otherwise do not respond to multicasted ICMPv6 Echo + Request messages. + + 4. Each time a new "alive" address is discovered, the corresponding + IID is combined with all the local prefixes, and the resulting + addresses are probed (with unicasted packets). This can help to + discover other addresses in use on the local network segment, + since the same IID is typically used with all the available + prefixes for the local network. + + NOTE: + The aforementioned scheme can fail to discover some addresses for + some implementations. For example, Mac OS X employs IPv6 + addresses embedding IEEE identifiers (rather than "temporary + addresses") when responding to packets destined to a link-local + multicast address, sourced from an on-link prefix. + +A.3. Implementation of an IPv6 Remote Address-Scanning Tool + + An IPv6 remote address-scanning tool could be implemented with the + following features: + + o The tool can be instructed to target specific address ranges + (e.g., 2001:db8::0-10:0-1000). + + o The tool can be instructed to scan for SLAAC addresses of a + specific vendor, such that only addresses embedding the + corresponding IEEE OUIs are probed. + + + + + +Gont & Chown Informational [Page 36] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + o The tool can be instructed to scan for SLAAC addresses that employ + a specific IEEE OUI or set of OUIs corresponding to a specific + vector. + + o The tool can be instructed to discover virtual machines, such that + a given IPv6 prefix is only scanned for the address patterns + resulting from virtual machines. + + o The tool can be instructed to scan for low-byte addresses. + + o The tool can be instructed to scan for wordy addresses, in which + case the tool selects addresses based on a local dictionary. + + o The tool can be instructed to scan for IPv6 addresses embedding + TCP/UDP service ports, in which case the tool selects addresses + based on a list of well-known service ports. + + o The tool can be specified to scan an IPv4 address range in use at + the target network, such that only IPv4-based IPv6 addresses are + scanned. + + The scan6 tool of [IPv6-Toolkit] implements all these techniques/ + features. Furthermore, when given a target domain name or sample + IPv6 address for a given prefix, the tool will try to infer the + address pattern in use at the target network, and reduce the address + search space accordingly. + +Acknowledgements + + The authors would like to thank Ray Hunter, who provided valuable + text that was readily incorporated into Section 4.2.1 of this + document. + + The authors would like to thank (in alphabetical order) Ivan Arce, + Alissa Cooper, Spencer Dawkins, Stephen Farrell, Wesley George, Marc + Heuse, Ray Hunter, Barry Leiba, Libor Polcak, Alvaro Retana, Tomoyuki + Sahara, Jan Schaumann, Arturo Servin, and Eric Vyncke for providing + valuable comments on earlier draft versions of this document. + + Fernando Gont would like to thank Jan Zorz of Go6 Lab + <http://go6lab.si/> and Jared Mauch of NTT America for providing + access to systems and networks that were employed to perform + experiments and measurements that helped to improve this document. + Additionally, he would like to thank SixXS <https://www.sixxs.net> + for providing IPv6 connectivity. + + + + + + +Gont & Chown Informational [Page 37] + +RFC 7707 IPv6 Reconnaissance March 2016 + + + Part of the contents of this document are based on the results of the + project "Security Assessment of the Internet Protocol version 6 + (IPv6)" [CPNI-IPv6], carried out by Fernando Gont on behalf of the UK + Centre for the Protection of National Infrastructure (CPNI). + + Fernando Gont would like to thank Daniel Bellomo (UNRC) for his + continued support. + +Authors' Addresses + + Fernando Gont + Huawei Technologies + Evaristo Carriego 2644 + Haedo, Provincia de Buenos Aires 1706 + Argentina + + Phone: +54 11 4650 8472 + Email: fgont@si6networks.com + URI: http://www.si6networks.com + + + Tim Chown + Jisc + Lumen House, Library Avenue + Harwell Oxford, Didcot. OX11 0SG + United Kingdom + + Email: tim.chown@jisc.ac.uk + + + + + + + + + + + + + + + + + + + + + + + +Gont & Chown Informational [Page 38] + |