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Network Working Group                                       T. KillaleaRequest for Comments: 3013                                    neart.orgBCP: 46                                                   November 2000Category: Best Current PracticeRecommended Internet Service Provider Security Services and ProceduresStatus of this Memo   This document specifies an Internet Best Current Practices for the   Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   The purpose of this document is to express what the engineering   community as represented by the IETF expects of Internet Service   Providers (ISPs) with respect to security.   It is not the intent of this document to define a set of requirements   that would be appropriate for all ISPs, but rather to raise awareness   among ISPs of the community's expectations, and to provide the   community with a framework for discussion of security expectations   with current and prospective service providers.Killalea                 Best Current Practice                  [Page 1]

RFC 3013                Recommended ISP Security           November 2000Table of Contents1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .21.1 Conventions Used in this Document. . . . . . . . . . . . . .32 Communication. . . . . . . . . . . . . . . . . . . . . . . . . .32.1 Contact Information. . . . . . . . . . . . . . . . . . . . .32.2 Information Sharing. . . . . . . . . . . . . . . . . . . . .42.3 Secure Channels. . . . . . . . . . . . . . . . . . . . . . .42.4 Notification of Vulnerabilities and Reporting Incidents. . .4     2.5 ISPs and Computer Security Incident Response Teams (CSIRTs). 53 Appropriate Use Policy . . . . . . . . . . . . . . . . . . . . .53.1 Announcement of Policy . . . . . . . . . . . . . . . . . . .63.2 Sanctions. . . . . . . . . . . . . . . . . . . . . . . . . .63.3 Data Protection. . . . . . . . . . . . . . . . . . . . . . .64 Network Infrastructure . . . . . . . . . . . . . . . . . . . . .64.1 Registry Data Maintenance. . . . . . . . . . . . . . . . . .64.2 Routing Infrastructure . . . . . . . . . . . . . . . . . . .74.3 Ingress Filtering on Source Address. . . . . . . . . . . . .74.4 Egress Filtering on Source Address . . . . . . . . . . . . .84.5 Route Filtering. . . . . . . . . . . . . . . . . . . . . . .84.6 Directed Broadcast . . . . . . . . . . . . . . . . . . . . .85 Systems Infrastructure . . . . . . . . . . . . . . . . . . . . .95.1 System Management. . . . . . . . . . . . . . . . . . . . . .95.2 No Systems on Transit Networks . . . . . . . . . . . . . . .95.3 Open Mail Relay. . . . . . . . . . . . . . . . . . . . . . .95.4 Message Submission . . . . . . . . . . . . . . . . . . . . .96 References . . . . . . . . . . . . . . . . . . . . . . . . . . .107 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . .128 Security Considerations. . . . . . . . . . . . . . . . . . . . .129 Author's Address . . . . . . . . . . . . . . . . . . . . . . . .1210 Full Copyright Statement. . . . . . . . . . . . . . . . . . . .131 Introduction   The purpose of this document is to express what the engineering   community as represented by the IETF expects of Internet Service   Providers (ISPs) with respect to security.  This document is   addressed to ISPs.   By informing ISPs of what this community hopes and expects of them,   the community hopes to encourage ISPs to become proactive in making   security not only a priority, but something to which they point with   pride when selling their services.   Under no circumstances is it the intention of this document to   dictate business practices.Killalea                 Best Current Practice                  [Page 2]

RFC 3013                Recommended ISP Security           November 2000   In this document we define ISPs to include organisations in the   business of providing Internet connectivity or other Internet   services including but not restricted to web hosting services,   content providers and e-mail services.  We do not include in our   definition of an ISP organisations providing those services for their   own purposes.   This document is offered as a set of recommendations to ISPs   regarding what security and attack management arrangements should be   supported, and as advice to users regarding what they should expect   from a high quality service provider.  It is in no sense normative in   its own right.  In time it is likely to become dated, and other   expectations may arise.  However, it does represent a snapshot of the   recommendations of a set of professionals in the field at a given   point in the development of the Internet and its technology.1.1 Conventions Used in this Document   The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",   and "MAY" in this document are to be interpreted as described in "Key   words for use in RFCs to Indicate Requirement Levels" [RFC2119].2 Communication   The community's most significant security-related expectations of   ISPs relate to the availability of communication channels for dealing   with security incidents.2.1 Contact Information   ISPs SHOULD adhere to [RFC2142], which defines the mailbox SECURITY   for network security issues, ABUSE for issues relating to   inappropriate public behaviour and NOC for issues relating to network   infrastructure.  It also lists additional mailboxes that are defined   for receiving queries and reports relating to specific services.   ISPs may consider using common URLs for expanded details on the above   (e.g.,http://www.ISP-name-here.net/security/).   In addition, ISPs have a duty to make sure that their contact   information, in Whois, in routing registries [RFC1786] or in any   other repository, is complete, accurate and reachable.Killalea                 Best Current Practice                  [Page 3]

RFC 3013                Recommended ISP Security           November 20002.2 Information Sharing   ISPs SHOULD have clear policies and procedures on the sharing of   information about a security incident with their customers, with   other ISPs, with Incident Response Teams, with law enforcement or   with the press and general public.   ISPs should have processes in place to deal with security incidents   that traverse the boundaries between them and other ISPs.2.3 Secure Channels   ISPs SHOULD be able to conduct such communication over a secure   channel.  Note, however, that in some jurisdictions secure channels   might not be permitted.2.4 Notification of Vulnerabilities and Reporting of Incidents   ISPs SHOULD be proactive in notifying customers of security   vulnerabilities in the services they provide.  In addition, as new   vulnerabilities in systems and software are discovered they should   indicate whether their services are threatened by these risks.   When security incidents occur that affect components of an ISP's   infrastructure the ISP should promptly report to their customers      -  who is coordinating response to the incident      -  the vulnerability      -  how service was affected      -  what is being done to respond to the incident      -  whether customer data may have been compromised      -  what is being done to eliminate the vulnerability      -  the expected schedule for response, assuming it can be         predicted   Many ISPs have established procedures for notifying customers of   outages and service degradation.  It is reasonable for the ISP to use   these channels for reporting security-related incidents.  In such   cases, the customer's security point of contact might not be the   person notified.  Rather, the normal point of contact will receive   the report.  Customers should be aware of this and make sure to route   such notifications appropriately.Killalea                 Best Current Practice                  [Page 4]

RFC 3013                Recommended ISP Security           November 20002.5 Incident Response and Computer Security Incident Response Teams   (CSIRTs)   A Computer Security Incident Response Team (CSIRT) is a team that   performs, coordinates, and supports the response to security   incidents that involve sites within a defined constituency.  The   Internet community's expectations of CSIRTs are described in   "Expectations for Computer Security Incident Response" [RFC2350].   Whether or not an ISP has a CSIRT, they should have a well-advertised   way to receive and handle reported incidents from their customers.   In addition, they should clearly document their capability to respond   to reported incidents, and should indicate if there is any CSIRT   whose constituency would include the customer and to whom incidents   could be reported.   Some ISPs have CSIRTs.  However it should not be assumed that either   the ISP's connectivity customers or a site being attacked by a   customer of that ISP can automatically avail themselves of the   services of the ISP's CSIRT.  ISP CSIRTs are frequently provided as   an added-cost service, with the team defining as their constituency   only those who specifically subscribe to (and perhaps pay for)   Incident Response services.   Thus it's important for ISPs to publish what incident response and   security resources they make available to customers, so that the   customers can define their incident response escalation chain BEFORE   an incident occurs.   Customers should find out whether their ISP has a CSIRT, and if so   what the charter, policies and services of that team are.  This   information is best expressed using the CSIRT template as shown inAppendix D of "Expectations for Computer Security Incident Response"   [RFC2350].3 Appropriate Use Policy   Every ISP SHOULD have an Appropriate Use Policy (AUP).   Whenever an ISP contracts with a customer to provide connectivity to   the Internet that contract should be governed by an AUP.  The AUP   should be reviewed each time the contract is up for renewal, and in   addition the ISP should proactively notify customers as policies are   updated.   An AUP should clearly identify what customers shall and shall not do   on the various components of a system or network, including the typeKillalea                 Best Current Practice                  [Page 5]

RFC 3013                Recommended ISP Security           November 2000   of traffic allowed on the networks.  The AUP should be as explicit as   possible to avoid ambiguity or misunderstanding.  For example, an AUP   might prohibit IP spoofing.3.1 Announcement of Policy   In addition to communicating their AUP to their customers ISPs should   publish their policy in a public place such as their web site so that   the community can be aware of what the ISP considers appropriate and   can know what action to expect in the event of inappropriate   behaviour.3.2 Sanctions   An AUP should be clear in stating what sanctions will be enforced in   the event of inappropriate behaviour.3.3 Data Protection   Many jurisdictions have Data Protection Legislation.  Where such   legislation applies, ISPs should consider the personal data they hold   and, if necessary, register themselves as Data Controllers and be   prepared to only use the data in accordance with the terms of the   legislation.  Given the global nature of the Internet ISPs that are   located where no such legislation exists should at least familiarise   themselves with the idea of Data Protection by reading a typical Data   Protection Act (e.g., [DPR1998]).4 Network Infrastructure   ISPs are responsible for managing the network infrastructure of the   Internet in such a way that it is      -  reasonably resistant to known security vulnerabilities      -  not easily hijacked by attackers for use in subsequent attacks4.1 Registry Data Maintenance   ISPs are commonly responsible for maintaining the data that is stored   in global repositories such as the Internet Routing Registry (IRR)   and the APNIC, ARIN and RIPE databases.  Updates to this data should   only be possible using strong authentication.   ISPs should publicly register the address space that they assign to   their customers so that there is more specific contact information   for the delegated space.Killalea                 Best Current Practice                  [Page 6]

RFC 3013                Recommended ISP Security           November 20004.2 Routing Infrastructure   An ISP's ability to route traffic to the correct destination may   depend on routing policy as configured in routing registries   [RFC1786].  If so, and if the registry supports it, they should   ensure that the registry information that they maintain can only be   updated using strong authentication, and that the authority to make   updates is appropriately restricted.   Due care should also be taken in determining in whose routing   announcements you place greater trust when a choice of routes are   available to a destination.  In the past bogus announcements have   resulted in traffic being 'black holed', or worse, hijacked.   BGP authentication [RFC2385] SHOULD be used with routing peers.4.3 Ingress Filtering on Source Address   The direction of such filtering is from the edge site (customer) to   the Internet.   Attackers frequently cover their tracks by using forged source   addresses.  To divert attention from their own site the source   address they choose will generally be from an innocent remote site or   indeed from those addresses that are allocated for private Internets   [RFC1918].  In addition, forged source addresses are frequently used   in spoof-based attacks in order to exploit a trust relationship   between hosts.   To reduce the incidence of attacks that rely on forged source   addresses ISPs should do the following.  At the boundary router with   each of their customers they should proactively filter all traffic   coming from the customer that has a source address of something other   than the addresses that have been assigned to that customer.  For a   more detailed discussion of this topic see [RFC2827].   There are (rare) circumstances where ingress filtering is not   currently possible, for example on large aggregation routers that   cannot take the additional load of applying packet filters.  In   addition, such filtering can cause difficulty for mobile users.   Hence, while the use of this technique to prevent spoofing is   strongly encouraged, it may not always be feasible.   In these rare cases where ingress filtering at the interface between   the customer and the ISP is not possible, the customer should be   encouraged to implement ingress filtering within their networks.  In   general filtering should be done as close to the actual hosts as   possible.Killalea                 Best Current Practice                  [Page 7]

RFC 3013                Recommended ISP Security           November 20004.4 Egress Filtering on Source Address   The direction of such filtering is from the Internet to the edge site   (customer).   There are many applications in widespread use on the Internet today   that grant trust to other hosts based only on ip address (e.g., the   Berkeley 'r' commands).  These are susceptible to IP spoofing, as   described in [CA-95.01.IP.spoofing].  In addition, there are   vulnerabilities that depend on the misuse of supposedly local   addresses, such as 'land' as described in [CA-97.28.Teardrop_Land].   To reduce the exposure of their customers to attacks that rely on   forged source addresses ISPs should do the following.  At the   boundary router with each of their customers they should proactively   filter all traffic going to the customer that has a source address of   any of the addresses that have been assigned to that customer.   The circumstances described in 4.3 in which ingress filtering isn't   feasible apply similarly to egress filtering.4.5 Route Filtering   Excessive routing updates can be leveraged by an attacker as a base   load on which to build a Denial of Service attack.  At the very least   they will result in performance degradation.   ISPs should filter the routing announcements they hear, for example   to ignore routes to addresses allocated for private Internets, to   avoid bogus routes and to implement "BGP Route Flap Dampening"   [RFC2439] and aggregation policy.   ISPs should implement techniques that reduce the risk of putting   excessive load on routing in other parts of the network.  These   include 'nailed up' routes, aggressive aggregation and route   dampening, all of which lower the impact on others when your internal   routing changes in a way that isn't relevant to them.4.6 Directed Broadcast   The IP protocol allows for directed broadcast, the sending of a   packet across the network to be broadcast on to a specific subnet.   Very few practical uses for this feature exist, but several different   security attacks (primarily Denial of Service attacks making use of   the packet multiplication effect of the broadcast) use it.   Therefore, routers connected to a broadcast medium MUST NOT be   configured to allow directed broadcasts onto that medium [RFC2644].Killalea                 Best Current Practice                  [Page 8]

RFC 3013                Recommended ISP Security           November 20005 Systems Infrastructure   The way an ISP manages their systems is crucial to the security and   reliability of their network.  A breach of their systems may   minimally lead to degraded performance or functionality, but could   lead to loss of data or the risk of traffic being eavesdropped (thus   leading to 'man-in-the-middle' attacks).   It's widely accepted that it's easier to build secure systems if   different services (such as mail, news and web-hosting) are kept on   separate systems.5.1 System Management   All systems that perform critical ISP functions such as mail, news   and web-hosting, should be restricted such that access to them is   only available to the administrators of those services.  That access   should be granted only following strong authentication, and should   take place over an encrypted link.  Only the ports on which those   services listen should be reachable from outside of the ISP's systems   networks.   ISPs should stay up to date for more secure methods of providing   services as they become available (e.g., IMAP/POP AUTHorize Extension   for Simple Challenge/Response, [RFC2195]).5.2 No Systems on Transit Networks   Systems should not be attached to transit network segments.5.3 Open Mail Relay   ISPs should take active steps to prevent their mail infrastructure   from being used by 'spammers' to inject Unsolicited Bulk E-mail (UBE)   while hiding the sender's identity [RFC2505].  While not all   preventive steps are appropriate for every site, the most effective   site-appropriate methods should be used.   ISPs should also strongly encourage their customers to take the   necessary steps to prevent this activity on their own systems.5.4 Message Submission   Message submissions should be authenticated using the AUTH SMTP   service extension as described in the "SMTP Service Extension for   Authentication" [RFC2554].Killalea                 Best Current Practice                  [Page 9]

RFC 3013                Recommended ISP Security           November 2000   SMTP AUTH is preferred over IP address-based submission restrictions   in that it gives the ISP's customers the flexibility of being able to   submit mail even when not connected through the ISP's network (for   example, while at work), is more resistant to spoofing, and can be   upgraded to newer authentication mechanisms as they become available.   In addition, to facilitate the enforcement of security policy, it is   strongly recommended that messages be submitted using the MAIL SUBMIT   port (587) as discussed in "Message Submission" [RFC2476], rather   than through the SMTP port (25).  In this way the SMTP port (25) can   be restricted to local delivery only.   The reason for this is to be able to differentiate between inbound   local delivery and relay (i.e., allow customers to send email via the   ISP's SMTP service to arbitrary receivers on the Internet).  Non-   authenticated SMTP should only be allowed for local delivery.   As more and more mail clients support both SMTP AUTH and the message   submission port (either explicitly or by configuring the SMTP port),   ISPs may find it useful to require that customers submit messages   using both the submission port and SMTP AUTH; permitting only inbound   mail on port 25.   These measures (SMTP AUTH and the submission port) not only protect   the ISP from serving as a UBE injection point via third-party relay,   but also help in tracking accountability for message submission in   the case where a customer sends UBE.6 References   [CA-95.01.IP.spoofing]   "IP Spoofing Attacks and Hijacked Terminal                            Connections",ftp://info.cert.org/pub/cert_advisories/   [CA-97.28.Teardrop_Land] "IP Denial-of-Service Attacks",ftp://info.cert.org/pub/cert_advisories/   [DPR1998]                The UK "Data Protection Act 1998 (c. 29)",http://www.hmso.gov.uk/acts/acts1998/19980029.htm   [RFC1786]                Bates, T., Gerich, E., Joncheray, L.,                            Jouanigot, J., Karrenberg, D., Terpstra, M.                            and J. Yu, "Representation of IP Routing                            Policies in a Routing Registry (ripe-81++)",RFC 1786, March 1995.Killalea                 Best Current Practice                 [Page 10]

RFC 3013                Recommended ISP Security           November 2000   [RFC1834]                Gargano, J. and K. Weiss, "Whois and Network                            Information Lookup Service",RFC 1834,                            August 1995.   [RFC1835]                Deutsch, P., Schoultz, R., Faltstrom, P. and                            C. Weider, "Architecture of the WHOIS++                            service",RFC 1835, August 1995.   [RFC1918]                Rekhter, Y., Moskowitz, B., Karrenberg, D.,                            de Groot, G. J. and E. Lear, "Address                            Allocation for Private Internets",BCP 5,RFC 1918, February 1996.   [RFC2119]                Bradner, S., "Key words for use in RFCs to                            Indicate Requirement Levels",BCP 14,RFC2119, March 1997.   [RFC2142]                Crocker, D., "Mailbox Names for Common                            Services, Roles and Functions",RFC 2142,                            May 1997.   [RFC2195]                Klensin, J., Catoe, R. and P. Krumviede,                            "IMAP/POP AUTHorize Extension for Simple                            Challenge/Response",RFC 2195, September                            1997.   [RFC2196]                Fraser, B., "Site Security Handbook", FYI 8,RFC 2196, September 1997.   [RFC2350]                Brownlee, N. and  E. Guttman, "Expectations                            for Computer Security Incident Response",BCP 21,RFC 2350, June 1998.   [RFC2385]                Heffernan, A., "Protection of BGP Sessions                            via the TCP MD5 Signature Option",RFC 2385,                            August 1998.   [RFC2439]                Chandra R., Govindan R. and C. Villamizar,                            "BGP Route Flap Damping",RFC 2439, November                            1998.   [RFC2476]                Gellens R. and J. Klensin, "Message                            Submission",RFC 2476, December 1998.   [RFC2505]                Lindberg, G., "Anti-Spam Recommendations for                            SMTP MTAs",BCP 30,RFC 2505, February 1999.Killalea                 Best Current Practice                 [Page 11]

RFC 3013                Recommended ISP Security           November 2000   [RFC2554]                Myers, J., "SMTP Service Extension for                            Authentication",RFC 2554, March 1999.   [RFC2644]                Senie, D., "Changing the Default for                            Directed Broadcasts in Routers",BCP 34,RFC2644, August 1999.   [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 2000.7 Acknowledgements   I gratefully acknowledge the constructive comments received from   Nevil Brownlee, Randy Bush, Bill Cheswick, Barbara Y. Fraser, Randall   Gellens, Erik Guttman, Larry J. Hughes Jr., Klaus-Peter Kossakowski,   Michael A. Patton, Don Stikvoort and Bill Woodcock.8 Security Considerations   This entire document discusses security issues.9 Author's Address   Tom Killalea   Lisi/n na Bro/n   Be/al A/tha na Muice   Co. Mhaigh Eo   IRELAND   Phone: +1 206 266-2196   EMail: tomk@neart.orgKillalea                 Best Current Practice                 [Page 12]

RFC 3013                Recommended ISP Security           November 200010 Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS 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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Killalea                 Best Current Practice                 [Page 13]