Routing Area WG P. Savola Internet-Draft CSC/FUNET Intended status: Informational June 13, 2006 Expires: December 15, 2006 Backbone Infrastructure Attacks and Protections draft-savola-rtgwg-backbone-attacks-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 15, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract A number of countermeasures for attacks against service provider backbone network infrastructure have been specified or proposed, each of them usually targeting a subset of the problem space. There has never been a more generic analysis of the actual problems, and which countermeasures are even necessary (and where). This document tries to provide that higher-level view. Savola Expires December 15, 2006 [Page 1] Internet-Draft Attacks Against Backbone June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Threat Model . . . . . . . . . . . . . . . . . . . . . . . 4 2. Attack Vectors . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Lower-layer Attacks . . . . . . . . . . . . . . . . . . . 5 2.2. Generic DoS on the Router . . . . . . . . . . . . . . . . 5 2.3. Generic DoS on a Link . . . . . . . . . . . . . . . . . . 5 2.4. Cryptographic Exhaustion Attacks . . . . . . . . . . . . . 6 2.5. Unauthorized Neighbor or Routing Attacks . . . . . . . . . 6 2.6. TCP RST Attacks . . . . . . . . . . . . . . . . . . . . . 7 2.7. ICMP Attacks . . . . . . . . . . . . . . . . . . . . . . . 7 3. Typical Countermeasures . . . . . . . . . . . . . . . . . . . 7 3.1. Address Filtering . . . . . . . . . . . . . . . . . . . . 7 3.2. Route Filtering . . . . . . . . . . . . . . . . . . . . . 7 3.3. GTSM . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4. TCP-MD5 and Other Custom Authentication . . . . . . . . . 9 3.5. IPsec and IKE . . . . . . . . . . . . . . . . . . . . . . 9 4. Protocol Analysis . . . . . . . . . . . . . . . . . . . . . . 9 4.1. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.3. BFD . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.4. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.5. Multicast Protocols (PIM, MSDP) . . . . . . . . . . . . . 11 5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . . . 16 Savola Expires December 15, 2006 [Page 2] Internet-Draft Attacks Against Backbone June 2006 1. Introduction A number of countermeasures for attacks against service provider backbone network infrastructure have been specified or proposed, each of them usually targeting a subset of the problem space. There has never been a more generic analysis of the actual problems, and which countermeasures are even necessary (and where). This document tries to provide that higher-level view. The scope of this document are backbone infrastructures and the critical protocols that are required to function for legitimate traffic to be correctly forwarded through the network. As such, other important services or applications required by infrastructure elements such as RADIUS, NTP, remote access, syslog, SNMP, and DNS are out of scope. All such components should be adequately protected through appropriate measures, the most important of which are proper address and route filtering and restricting authorized access. Additionally, the network might run additional routing protocols that are not described in this memo, such as (G)MPLS, RSVP-TE or LDP. 1.1. Abbreviations We exclude the common abbreviations such as TCP, ICMP and DNS. BGP Border Gateway Protocol BFD Bidirectional Forwarding Detection DoS Denial of Service DSCP DiffServ Code Point GTSM Generalized TTL Security Mechanism IGP Interior Gateway Protocol IKE Internet Key Exchange IRR Internet Routing Registry IS-IS Integrated System - Integrated System (routing protocol) LDP Label Distribution Protocol (G)MPLS (Generalized) Multi-Protocol Label Switching MSDP Multicast Source Discovery Protocol NTP Network Time Protocol OSPF Open Shortest Path First PIM Protocol Independent Multicast RADIUS Remote Authentication Dial-In User Service RSVP-TE Resource Reservation Protocol - Traffic Engineering SNMP Simple Network Management Protocol Savola Expires December 15, 2006 [Page 3] Internet-Draft Attacks Against Backbone June 2006 1.2. Assumptions This document assumes that the service provider is doing at least some form of address filtering at its border devices, i.e., by ensuring that only the infrastructure nodes can use infrastructure source IP addresses to talk to the other nodes in the infrastructure. So, for example, if a router sees an IP packet coming from a source address assigned to another router in the backbone, it can be sure the packet has been originated inside the backbone (assuming the physical security or nodes in the backbone have not been subverted). This requirement can be satisfied by applying ingress filtering at all the ISP borders [RFC2827][RFC3704], but just filtering infrastructure source IP addresses from the outside is also sufficient. Some may even implement this by blocking access to the infrastructure destination addresses at the border, but this document doesn't describe this approach as that has a number of other issues. Current operational practices are described in [I-D.ietf-opsec-current-practices]; while almost all ISPs are capable of employing data plane filtering at the edges, at least one major ISP is known not do be able to due to legacy hardware limitations. Various filtering capabilities have been discussed at more length in [I-D.ietf-opsec-filter-caps]. If this requirement cannot be satisfied, other approaches are warranted. For example, [I-D.zinin-rtg-dos] suggested an alternative (and in any case, provides good analysis); IPsec-protecting all the control traffic may be an option if "all bets are off". 1.3. Threat Model In the context of this document, threats are assumed to come from external sources, either from customers or other networks. The typical attacks are either meant to cause some form of denial of service or to hijack or gain access to a service, such as: o DoS attacks directed at infrastructure (e.g., TCP RSTs, ICMP attacks), o DoS attacks directed at someone else but cause harm (e.g., too much traffic exceeds forwarding or control processor capacity), or o Hijacking attacks (e.g., unauthorized routing advertisement, access control attempt with a spoofed address). Other possible attack vectors include inside attacks (e.g., compromised personnel or inadequately protected infrastructure Savola Expires December 15, 2006 [Page 4] Internet-Draft Attacks Against Backbone June 2006 device) and lower-layer attacks as described in Section 2.1. While the insider attack could be devastating, it can be mitigated by access controls and automatic configuration audits. As such the first order priority problems typically come from external sources. 2. Attack Vectors This Section describes the most obvious attack vectors. 2.1. Lower-layer Attacks If an attacker has access to a (physical) link, it can obviously cause downtime for the link. In many cases the downtime is not a critical threat, as it can be quickly noticed, traffic rerouted, and the problem fixed. Some ISPs are more concerned about other forms of attacks: insertion of eavesdropping or man-in-the-middle devices. Fortunately, installing such would require downtime, and insertion could be noticeable, e.g., as an unscheduled issue gets fixed on its own. However, a lower-layer attack is not specific to routing protocols. An attacker could just violate integrity or confidentiality of regular packets, instead of tampering with routing. As such, if a lower-layer attack is deemed a concern, full protection for all the traffic should be provided and therefore this threat is not addressed in this document. 2.2. Generic DoS on the Router A typical attack is to overload a router using various techniques, e.g., by sending traffic exceeding the router's forwarding capacity, sending special transit packets that go through a "slow-path" processing (such functions may also come with problems of their own [BLOCKED]), or by sending some packets directed at the router itself. Many of these techniques can be mitigated using implementation- specific rate-limiting mechanisms, so they are not addressed further in this memo. However, protocol designers should be advised to avoid any designs that require noticing and processing any special packets from the transit traffic (e.g., messages marked with router alert option). 2.3. Generic DoS on a Link Overloading the capacity of a link is often more difficult to prevent than a router DoS. Traffic is typically not automatically rerouted and even if it did, doing so could make the issue worse unless there Savola Expires December 15, 2006 [Page 5] Internet-Draft Attacks Against Backbone June 2006 is ample spare capacity. Mitigation methods include monitoring the usage status of links, prioritizing or deprioritizing certain kinds of traffic using DSCPs, or devising some form of rate-limiters. 2.4. Cryptographic Exhaustion Attacks A special form of DoS are attacks which target a protocol that uses cryptographic mechanisms, for example TCP-MD5 or IPsec. The attacker sends valid protocol messages with cryptographic signatures or other properties to the router, which is forced to perform cryptographic validation of the message. If the cryptographic operations are computationally expensive, the attack might succeed easier than with other generic DoS mechanisms. Cryptographic protocols employing primitives such as stateless cookies, puzzles or return routability are typically more resistant to this kind of attacks. Some implementation-specific mitigation techniques (rate-limiting etc.) have been deployed, but as this affects the choice of a countermeasure due to protocol design. 2.5. Unauthorized Neighbor or Routing Attacks Unauthorized nodes can obtain a routing protocol adjacency on links where an IGP has been enabled by misconfiguration, or where authentication is not used. This may result in many different kinds of attacks, for example traffic redirection [I-D.ietf-rpsec-routing-threats]. At least in theory, while it may not be possible to establish an adjacency from outside the link, it may be possible to inject packets as if the adjacency had been established (e.g., OSPF in Section 3.1.2 of [I-D.ietf-rpsec-ospf-vuln]). Protocols such as BGP and MSDP that process routing information from untrusted, external sources may also be attacked, for example by an unauthorized advertisement of a prefix. Special care needs to be made to ensure that unauthorized neighbors are prevented (e.g., by regular configuration audits and OSPF protocol filtering at borders). On the other hand, routing attack threats from valid neighbors can be minimized via appropriate route filtering. Savola Expires December 15, 2006 [Page 6] Internet-Draft Attacks Against Backbone June 2006 2.6. TCP RST Attacks TCP sessions can be closed by attackers that can send a TCP RST packet with guessed spoofed endpoint identifiers and a sufficiently close sequence number. The attacks and defenses have been described at length in [I-D.ietf-tcpm-tcp-antispoof]. One particular approach is modifying the TCP state machine [I-D.ietf-tcpm-tcpsecure]. 2.7. ICMP Attacks A slightly newer attack is employing ICMP by sending an ICMP type that indicates a hard error condition. ICMP errors must be propagated to applications, and most applications heed the errors as they should by closing a connection or session. ICMP attacks and defenses against TCP have been extensively described in [I-D.ietf-tcpm-icmp-attacks]. It is also possible to execute ICMP attacks against other protocols such as UDP or IPsec, but the impact and whether/how these protocols demultiplex received errors have not been extensively studied. IPsec is protected by ICMP attacks through a lot of assumptions (e.g., that only ICMP errors from the end-point are accepted) or manual configuration. 3. Typical Countermeasures This Section describes some of the most common countermeasures applied today. This just introduces the techniques; the afforded protection is analyzed in Section 4 in the context of each protocol. 3.1. Address Filtering As described in the first section, this document assumes that the internal infrastructure is secure from spoofed messages that purport to come from inside the infrastructure. More fine-grained, router- specific filters are sometimes deployed as well. It is possible to hide the infrastructure by using private or non- advertised addressing, but this has numerous drawbacks such as breaking address filtering and traceroute, not protecting from the ISP's customers that use a default route, etc. so this document doesn't recommand doing so. 3.2. Route Filtering Similar principles as used in address filtering can be used to mitigate routing attacks. Specifically, reject any equal or more Savola Expires December 15, 2006 [Page 7] Internet-Draft Attacks Against Backbone June 2006 specific incoming routing advertisements to the ISP's address space unless explicitly authorized. Further, monitor the filtered prefixes and use public services (such as RIPE's MyASN [MYASN]) to monitor the correctness of advertisements globally. In addition, especially in regions where the operational practice is to keep Internet Routing Registry (IRR) in sync, it may be possible to restrict the prefixes accepted from a peer or a customer to an automatically generated list. In any case, many operators define a maximum prefix limit per peer (which typically resets the session if exceeded) to prevent misconfiguration or overload attacks. As with address filtering, such routing advertisements might still be processed by other networks, but at least these steps prevent hijacking inside the ISP's own network and allow monitoring of most unauthorized attempts. 3.3. GTSM GTSM [I-D.ietf-rtgwg-rfc3682bis] is a technique where the sender of a packet sets the TTL/Hop Count to 255 and the receiver verifies it's still 255 (or some other preconfigured value). GTSM can be used to protect from off-link attacks (especially spoofing). This applies when GTSM-enabled control traffic is inside a single link: any packets coming from outside the link can summarily be discarded as they have a TTL/Hop Count smaller than 255. The open issue at the moment is how GTSM handles TCP RSTs. I.e., should it require that RSTs for a GTSM-enabled session should be sent with TTL=255 and verified to come with TTL=255 (or a configured value)? Do implementations already do this? Is there a sensible transition plan or need to make a change if any? Note that this has only limited impact on GTSM's security as other TCP RST mitigation techniques still apply. NOTE IN DRAFT: the following paragraph should be removed in a future revision, to be placed to the GTSMbis draft. We suggest that the GTSM spec is amended so that TCP RSTs relating to a GTSM-enabled protocol port MUST be sent with TTL=255. (Note that this will require a kernel modification, and a means to specify to the kernel which ports relate to GTSM.). The recipient's behaviour SHOULD be configurable, and it is RECOMMENDED that the default be to discard messages where TTL is not 255 (or 255-TrustRadius). Savola Expires December 15, 2006 [Page 8] Internet-Draft Attacks Against Backbone June 2006 3.4. TCP-MD5 and Other Custom Authentication At least BGP, MSDP, and LDP are able to use the TCP-MD5 signature option to verify the authenticity of control packets. TCP-MD5 uses manually configured static keys, so changing them typically resets the protocol session, so the solution is sub-optimal in cases where the security procedures require (e.g., after an employee leaves the organization) that the keys must be easily and often changeable. Using TCP-MD5 and other similar authentication mechanisms (e.g., for IGPs or BFD) also opens an attack vector for cryptographic exhaustion attacks unless implementations have appropriate mechanisms to throttle or otherwise manage heavy cryptographic operations. 3.5. IPsec and IKE IPsec and IKE have been proposed as a more comprehensive countermeasure, but these protocols also require a lot of heavyweight protocol machinery, lots of configuration, and cryptographic processing. Vendors have also expressed difficulty in applying IPsec to control traffic protection. 4. Protocol Analysis This Section briefly discusses the protocol-specific attack properties below. ICMP attacks apply to all the IP protocols at least to some degree. There is no reasonable way to appropriately protect from these attacks by operative methods: the vendors should implement countermeasures described in [I-D.ietf-tcpm-icmp-attacks] to mitigate these attacks. 4.1. OSPF OSPF attacks have already been analyzed [I-D.ietf-rpsec-ospf-vuln]. In this context the most important of them are: (1) preventing misconfiguration and unauthorized neighbors, and (2) ensuring off- path directed attacks as described in Section 3.1.2 of [I-D.ietf-rpsec-ospf-vuln]. The former requires configuration change procedures and regular audits of OSPF configuration, and disabling OSPF adjacencies on customer-facing links, or adding authentication when there are multiple routers. The latter requires using OSPF authentication, dropping all OSPF traffic at all the borders, or moving to another, less vulnerable protocol (e.g., IS-IS). Savola Expires December 15, 2006 [Page 9] Internet-Draft Attacks Against Backbone June 2006 OSPF is also used to some degree with provider-provisioned VPNs by the customers. In such scenarios, strict route filtering needs to be applied to ensure only the valid prefixes are accepted. 4.2. IS-IS Routing IP with IS-IS has gained popularity in the backbone networks lately. As IS-IS does not use IP, it is sufficient to prevent misconfiguration and unauthorized neighbors. Thus most of the attacks and countermeasures of OSPF apply to IS-IS as well: configuration change procedures and regular configuration audits and disabling IS-IS adjacencies on customer-facing links, or adding authentication when there are multiple routers. 4.3. BFD Bidirectional Forwarding Detection (BFD) detects faults in the forwarding path between two endpoints. As a generic mechanism, it can be applied to a number of protocols (e.g., OSPF, IS-IS, BGP, MPLS, or static routes). When BFD is in use for a single-hop scenario, it uses GTSM to protect from off-link attackers. Authentication can also be used for example on untrusted links. 4.4. BGP Internal BGP sessions run between loopback addresses. There is no need to run TCP-MD5 for outsider protection as address filtering will avoid TCP RST attacks. External BGP sessions may run multi-hop between loopback addresses or single-hop between interface addresses. The latter case is much more common and easier to protect and applying GTSM provides first-order resistance to off-link attackers. In any case, assuming address filtering, the session can only be reset by the peer, or by attacks from the direction of the peer's network (e.g., through lack of peer's border filtering). One can therefore question the necessity of further protection as the peer can only shoot itself in the foot by killing the BGP session or allowing the BGP session be killed through negligence. If the link is not trusted (e.g., in some large Ethernet-based Internet Exchange points), it may also be desirable to ensure that peers are not able to reset others' sessions, so a mechanism like TCP-MD5 may be appropriate. One should note that the security requirements are not necessarily very high as the attacker should Savola Expires December 15, 2006 [Page 10] Internet-Draft Attacks Against Backbone June 2006 already be easily traceable on a single link, and thus re-keying may not be worth the trouble. As BGP processes data heard from external sources, the routing data can be modified in numerous ways, e.g., to create arbitrarily complex advertisements using path attributes to crash naive BGP implementations. These and many other BGP attacks are described in [RFC4272]. Techniques described in Section 3.2 can mitigate the attack vectors to some degree, but a more comprehensive solution to securing routing data is needed. 4.5. Multicast Protocols (PIM, MSDP) Multicast routing is typically achieved by PIM-SM [I-D.ietf-mboned-routingarch]. MSDP is used for IPv4 source discovery. Multicast routing protocol threats have been analyzed separately in [I-D.ietf-mboned-mroutesec] (backbone perspective) and [I-D.savola-pim-lasthop-threats] (last-hop perspective). In summary, most of the multicast threats pertain to overloading control processors via too much state. Implementation-specific rate- limiters can help in mitigating the risk. If resetting MSDP sessions is a concern, TCP-MD5 option similar to BGP can be used. Address filtering can be applied in particular in PIM Unicast-Register message decapsulation; other messages use multicast and already employ reverse path forwarding checks. 5. Summary IGPs require a great deal of care to ensure that they are not enabled on links where they shouldn't be. Preventing external OSPF attacks also requires OSPF authentication everywhere or filtering OSPF packets at the edges. ICMP attacks are able to cause a great deal of harm to almost all the protocols, including IPsec, and there is little to do to mitigate the risk except to implement enhanced ICMP payload verification/ processing techniques. More study of the impact on connectionless protocols and IPsec should be conducted. With border address filtering in place, internal sessions are reasonably safe. With additional GTSM protection, external private interconnection links are also reasonably safe, as the session can only be reset by the neighbor or due to lack of filtering, someone through the neighbor's network. TCP-MD5 protection is most appropriate for Internet Exchange points with multiple neighbors or multihop eBGP sessions, but it's worth remembering that the security Savola Expires December 15, 2006 [Page 11] Internet-Draft Attacks Against Backbone June 2006 requirements for the solution are not very high as the attackers have very strict topological restrictions. IPsec and IKE are obviously an option for heavy-weight protection, but impractical (yet) due to configuration complexity and processing overhead. Simplifications in configuration, implementation, and cryptographic hardware offloading might help the situation for the cases where the use of heavier protection (e.g., possibly Internet Exchange points) could be warranted. 6. IANA Considerations This memo makes no request to IANA. 7. Acknowledgements George Jones suggested improvements to the initial version of this draft. Further feedback was received from Sean P. Turner, Seo Boon NG, Warren Kumari, Hank Nussbacher, and Jonathan Trostle. 8. Security Considerations This document does not define a protocol but rather describes and analyzes the security properties and countermeasures in existing service provider backbone network infrastructures. The most important issues that should be noted are its security assumptions: o The main concern is an external attack (from customers or some other network); lower-layer attacks are not considered a particular concern for routing protocols. o We require at least certain degree of address filtering at borders, or else all bets are off. o Generic DoS attacks against routers can be mitigated using implementation-specific measures. There are a number of activities network operators have to do in order to protect the network (e.g., filtering OSPF packets at the edges or auditing IGP configurations). There are also lessons to be learned for protocol designers (e.g., OSPF external attacks, ICMP attacks against non-TCP, use of GTSM). Many of the issues listed also depend on vendors to implement effective, vendor-specific rate- Savola Expires December 15, 2006 [Page 12] Internet-Draft Attacks Against Backbone June 2006 limiting techniques. 9. References 9.1. Normative References [I-D.ietf-mboned-mroutesec] Savola, P., Lehtonen, R., and D. Meyer, "PIM-SM Multicast Routing Security Issues and Enhancements", draft-ietf-mboned-mroutesec-04 (work in progress), October 2004. [I-D.ietf-opsec-current-practices] Kaeo, M., "Operational Security Current Practices", draft-ietf-opsec-current-practices-03 (work in progress), May 2006. [I-D.ietf-rpsec-ospf-vuln] Jones, E. and O. Moigne, "OSPF Security Vulnerabilities Analysis", draft-ietf-rpsec-ospf-vuln-01 (work in progress), December 2004. [I-D.ietf-rpsec-routing-threats] Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to Routing Protocols", draft-ietf-rpsec-routing-threats-07 (work in progress), October 2004. [I-D.ietf-rtgwg-rfc3682bis] Gill, V., "The Generalized TTL Security Mechanism (GTSM)", draft-ietf-rtgwg-rfc3682bis-05 (work in progress), April 2005. [I-D.ietf-tcpm-icmp-attacks] Gont, F., "ICMP attacks against TCP", draft-ietf-tcpm-icmp-attacks-00 (work in progress), February 2006. [I-D.ietf-tcpm-tcp-antispoof] Touch, J., "Defending TCP Against Spoofing Attacks", draft-ietf-tcpm-tcp-antispoof-04 (work in progress), May 2006. [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed Savola Expires December 15, 2006 [Page 13] Internet-Draft Attacks Against Backbone June 2006 Networks", BCP 84, RFC 3704, March 2004. [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, January 2006. 9.2. Informative References [BLOCKED] Cisco Systems, "Cisco Security Advisory: Cisco IOS Interface Blocked by IPv4 Packets", 2004, . [I-D.ietf-mboned-routingarch] Savola, P., "Overview of the Internet Multicast Routing Architecture", draft-ietf-mboned-routingarch-03 (work in progress), March 2006. [I-D.ietf-opsec-filter-caps] Morrow, C., "Filtering Capabilities for IP Network Infrastructure", draft-ietf-opsec-filter-caps-01 (work in progress), May 2006. [I-D.ietf-tcpm-tcpsecure] Stewart, R. and M. Dalal, "Improving TCP's Robustness to Blind In-Window Attacks", draft-ietf-tcpm-tcpsecure-04 (work in progress), February 2006. [I-D.savola-pim-lasthop-threats] Savola, P., "Last-hop Threats to Protocol Independent Multicast (PIM)", draft-savola-pim-lasthop-threats-01 (work in progress), January 2005. [I-D.zinin-rtg-dos] Zinin, A., "Protecting Internet Routing Infrastructure from Outsider DoS Attacks", draft-zinin-rtg-dos-02 (work in progress), May 2005. [MYASN] RIPE NCC, "MyASn System", . Savola Expires December 15, 2006 [Page 14] Internet-Draft Attacks Against Backbone June 2006 Author's Address Pekka Savola CSC/FUNET Espoo Finland Email: psavola@funet.fi Savola Expires December 15, 2006 [Page 15] Internet-Draft Attacks Against Backbone June 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Savola Expires December 15, 2006 [Page 16]