MARF Working Group                                               J. Falk
Internet-Draft                                               Return Path
Updates: 5965 (if approved)                            M. Kucherawy, Ed.
Intended status: Standards Track                               Cloudmark
Expires: July 28, 2012                                  January 25, 2012

 Creation and Use of Email Feedback Reports: An Applicability Statement
                  for the Abuse Reporting Format (ARF)


   RFC 5965 defines an extensible, machine-readable format intended for
   mail operators to report feedback about received email to other
   parties.  This document describes common methods for utilizing this
   format for abuse reporting.  Mailbox Providers of any size, mail
   sending entities, and end users can use these methods as a basis to
   create procedures that best suit them.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on July 28, 2012.

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   document authors.  All rights reserved.

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   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.

1.  Introduction

   The Abuse Reporting Format (ARF) was initially developed for two very
   specific use cases.  Initially, it was intended to be used for
   reporting feedback between large email operators, or from large email
   operators to end user network access operators, any of whom could be
   presumed to have automated abuse-handling systems.  Secondarily, it
   is used by those same large mail operators to send those same reports
   to other entities, including those involved in sending bulk email for
   commercial purposes.  In either case, the reports would be triggered
   by direct end user action such as clicking on a "report spam" button
   in their email client.

   Though other uses for the format defined in [RFC5965] have been
   discussed (and may be documented similarly in the future), abuse
   remains the primary application.

   The purpose for reporting abusive messages is to stop recurrences.
   The methods described in this document focus on automating abuse
   reporting as much as practical, so as to minimize the work of a
   site's abuse team.  There are further reasons why abuse feedback
   generation is worthwhile, such as instruction of mail filters or
   reputation trackers, or to initiate investigations of particularly
   egregious abuses.  These other applications are not discussed in this

   Further introduction to this topic may be found in [RFC6449].

2.  Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119], and are
   intended to replace the Requirement Levels described in Section 3.3
   of [RFC2026].

   Some of the terminology used in this document is taken from

   "Mailbox Provider" refers to an organization that accepts, stores,
   and offers access to [RFC5322] messages ("email messages") for end
   users.  Such an organization has typically implemented SMTP

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   ([RFC5321]), and might provide access to messages through IMAP
   ([RFC3501]), POP ([RFC1939]), a proprietary interface designed for
   HTTP ([RFC2616]), or a proprietary protocol.

3.  Applicability Statement

   [RFC Editor: please remove this section prior to publication.]

   NOTE TO IESG: This document is part of the experiment to reintroduce
   Applicability Statements, as defined in Section 3.2 of [RFC2026], to
   the Applications Area.

4.  Discussion

   [RFC Editor: please remove this section prior to publication.]

   This document is being discussed within the IETF MARF Working Group,
   on the mailing list.

5.  Solicited and Unsolicited Reports

   The original application of [RFC5965], and still by far the most
   common, is when two mail systems make a private agreement to exchange
   abuse reports, usually reports due to recipients manually reporting
   messages as spam.  We refer to these as solicited reports.

   Other uses for ARF involve reports sent between parties that don't
   know each other, with the recipient address typically being
   abuse@domain (see [RFC2142]), looked up via WHOIS, or using other
   heuristics.  The reports may be manual, or automated due to hitting
   spam traps, or caused by anything else that the sender of the report
   considers to merit an abuse report.  Abuse addresses in WHOIS records
   of the source IP and of the domain found in the results of a PTR
   ("reverse lookup") query on that address are likely reasonable
   candidates for receiving feedback about the message, although
   automated parsing may be difficult.

   However, it is inadvisable to generate automated reports based on
   inline content analysis tools that apply subjective evaluation rules.
   This can cause reports that, because of their subjective nature, are
   not actionable by report receivers, which wastes valuable operator
   time in processing them.

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6.  Creating and Sending Complaint-Based Solicited Reports

   1.  A Mailbox Provider receives reports of abusive or unwanted mail
       from its users, most often by providing a "report spam" button
       (or similar nomenclature) in the MUA.  The method of transferring
       this message and any associated metadata from the MUA to the
       Mailbox Provider's ARF processing system is not defined by any
       standards document, but is discussed further in Section 3.2 of
       [RFC6449].  Policy concerns related to the collection of this
       data are discussed in Section 3.4 of that document.
   2.  The Mailbox Provider SHOULD process the reports to improve its
       spam filtering systems.  The design of these systems is discussed
       in [RFC2505] and elsewhere.
   3.  The Mailbox Provider SHOULD send reports to relevant parties who
       have requested to receive such reports.  The reports MUST be
       formatted per [RFC5965], and transmitted as an email message
       ([RFC5322]), typically using SMTP ([RFC5321]).  The process
       whereby such parties may request the reports is discussed in
       Section 3.5 of [RFC6449].
   4.  The reports SHOULD use "Feedback-Type: abuse", but MAY use other
       types as appropriate.  However, the Mailbox Provider generating
       the reports SHOULD NOT assume that the operator receiving the
       reports will treat different Feedback-Types differently.
   5.  The reports SHOULD include the following optional fields whenever
       practical: Original-Mail-From, Arrival-Date, Source-IP, Original-
       Rcpt-To.  Other optional fields MAY be included, as the
       implementer feels is appropriate.
   6.  Ongoing maintenance of an ARF processing system is discussed in
       Section 3.6 of [RFC6449].
   7.  Reports MAY be subjected to redaction of user-identifiable data
       as described in [I-D.IETF-MARF-REDACTION].

7.  Receiving and Processing Complaint-Based Solicited Reports

   1.  At the time this document is being written, for the use cases
       described here, mail operators need to proactively request a
       stream of ARF reports from Mailbox Providers.  Recommendations
       for preparing to make that request are discussed in Section 4.1
       of [RFC6449].
   2.  Mail operators MUST be prepared to receive reports formatted per
       [RFC5965] as email messages ([RFC5322]) over SMTP ([RFC5321]).
       These and other types of email messages that may be received are
       discussed in Section 4.2 of [RFC6449].
   3.  Mail operators need to consider the idea of automating report
       processing.  Discussion of this can be found in Section 4.4 of

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   4.  That system MUST accept all Feedback-Types defined in [RFC5965]
       or extensions to it, but implementers SHOULD NOT assume that
       Mailbox Providers will make use of any Feedback-Type other than
       "abuse".  Additional logic may be required to separate different
       types of abuse reports after receipt.
   5.  Implementers SHOULD NOT expect all Mailbox Providers to include
       the same optional fields.
   6.  Actions that mail operators might take upon receiving a report
       (or multiple reports) are discussed in Section 4.3 of [RFC6449].
   7.  Reports MAY be subjected to redaction of user-identifiable data
       as described in [I-D.IETF-MARF-REDACTION].

8.  Generating and Handling Unsolicited Reports

   1.   Systems that generate unsolicited reports SHOULD ensure that the
        criteria used to decide what messages to report accurately
        identify messages that the generating entity believes in good
        faith are abusive.  Such criteria might include direct complaint
        submissions from MUAs, reports triggered by mail sent to "spam
        trap" or "honeypot" addresses, reports of authentication
        failures, and virus reports.  (These applications might be
        described in future IETF documents.)  Systems SHOULD NOT report
        all mail sent from a particular sender merely because some of it
        is determined to be abusive.
   2.   With respect to authentication failures, these could occur for
        legitimate reasons outside of the control of the author.  A
        report generator SHOULD be cautious to generate reports only in
        those cases where doing so highlights a serious problem, such as
        an ADSP ([RFC5617]) failure for a high-value spam target.
   3.   MUAs SHOULD NOT generate abuse reports directly to entities
        found in the message or by queries to WHOIS or other heuristic
        means.  Rather, the MUA should signal, by some means, the
        service provider to which it connects to generate such a report.
   4.   Report generators SHOULD send reports to recipients that are
        both responsible for the messages and are able to do something
        about them, and SHOULD NOT send reports to recipients that are
        uninvolved or only peripherally involved.  For example, they
        SHOULD NOT send reports to the operator of every Autonomous
        System in the path between the apparent originating system and
        the operator generating the report.
   5.   Where an abusive message is signed using a domain-level
        authentication technology such as DKIM ([RFC6376]) or SPF
        ([RFC4408]), the domain that has been verified by the
        authentication mechanism is likely a reasonable candidate for
        receiving feedback about the message.  However, this is not
        universally true, since sometimes the domain thus verified
        exists only to distinguish one stream of mail from another (see

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        Section 2.5 of [RFC6377]), and cannot actually receive email.
   6.   Recipients of unsolicited ARF reports SHOULD, in general, handle
        them the same way as any other abuse reports.  However, they MAY
        take advantage of the standardized parts of the ARF format to
        automate processing.  Lacking knowledge about the sender of the
        report, they SHOULD separate valid from invalid reports by, for
        example, looking for references to IP ranges, domains, and
        mailboxes for which the recipient organization is responsible in
        the copy of the reported message, and by correlating multiple
        reports of similar messages to identify bulk senders.
   7.   Reports SHOULD use "Feedback-Type: abuse", but MAY use other
        types as appropriate.  However, the Mailbox Provider generating
        the reports SHOULD NOT assume that the operator receiving the
        reports will treat different Feedback-Types differently.
   8.   Reports SHOULD include the following optional fields whenever
        practical: Original-Mail-From, Arrival-Date, Source-IP,
        Original-Rcpt-To.  Other optional fields MAY be included, as the
        implementer feels is appropriate.
   9.   Published abuse mailbox addresses SHOULD NOT reject messages not
        in the ARF format, as generation of ARF messages can
        occasionally be unavailable or not applicable.  Nevertheless,
        some large messaging service providers specifically request that
        abuse reports be sent to them in ARF format.  Experience of
        systems that send abuse reports in ARF format suggests that even
        automated recipient systems that haven't asked for ARF format
        reports handle them at least as well as any other format such as
        plain text, with or without a copy of the message attached.
        This suggests use of ARF is advisable in most contexts.
   10.  This is, however, not universally true.  Anyone sending
        unsolicited reports in ARF format can legitimately presume that
        recipients will not be able to see the ARF metadata (i.e., those
        elements present in the second part of the report), and instead
        MAY include all information needed in the human readable (first,
        text/plain) section of the report.  Further, they MAY ensure
        that the report is readable when viewed as plain text, to give
        low-end ticketing systems as much assistance as possible.
        Finally, they need to be aware that the report could be
        discarded or ignored due to failure to take these steps in the
        most extreme cases.
   11.  Although [RFC6449] suggests that replying to feedback is not
        useful, in the case of receipt of ARF reports where no feedback
        arrangement has been established, a reply might be desirable to
        indicate that the complaint will result in action, heading off
        more severe filtering from the report generator.  Thus, a report
        generator sending unsolicited reports SHOULD ensure that a reply
        to such a report can be received.  Where an unsolicited report
        results in the establishment of contact with a responsible and
        responsive party, this can be saved for future complaint

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        handling and possible establishment of a formal (solicited)
        feedback arrangement.
   12.  Unsolicited reports will have no meaning if sent to abuse
        reporting addresses belonging to the abusive parties themselves.
        Reports SHOULD NOT be sent to such addresses if they can be
        identified beforehand.

9.  IANA Considerations

   [RFC Editor: please remove this section prior to publication.]

   This document has no IANA actions.

10.  Security Considerations

   Implementers are strongly urged to review, at a minimum, the Security
   Considerations sections of [RFC5965] and [RFC6449].

   Report generators that relay user complaints directly, rather than by
   reference to a stored message (e.g., IMAP or POP), could be duped
   into sending a complaint about a message that the complaining user
   never actually received, as an attack on the purported originator of
   the falsified message.  Report generators need to be resilient to
   such attack methods.

11.  Acknowledgements

   The author and editor wish to thank Steve Atkins, John Levine, Shmuel
   Metz, and Alessandro Vesely for their contributions to this memo.

   All of the Best Practices referenced by this document are found in
   [RFC6449], written within the Collaboration Committee of the
   Messaging Anti-Abuse Working Group (MAAWG).

   Finally, the original author wishes to thank the doctors and staff at
   the University of Texas MD Anderson Cancer Center for doing what they

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              October 2008.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              October 2008.

   [RFC5598]  Crocker, D., "Internet Mail Architecture", RFC 5598,
              July 2009.

   [RFC5965]  Shafranovich, Y., Levine, J., and M. Kucherawy, "An
              Extensible Format for Email Feedback Reports", RFC 5965,
              August 2010.

12.2.  Informative References

              Falk, JD. and M. Kucherawy, Ed., "Redaction of Potentially
              Sensitive Data from Mail Abuse Reports",
              I-D draft-ietf-marf-redaction, March 2011.

   [RFC1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
              STD 53, RFC 1939, May 1996.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

              FUNCTIONS", RFC 2142, May 1997.

   [RFC2505]  Lindberg, G., "Anti-Spam Recommendations for SMTP MTAs",
              BCP 30, RFC 2505, February 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

              4rev1", RFC 3501, March 2003.

   [RFC4408]  Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)
              for Authorizing Use of Domains in E-Mail, Version 1",
              RFC 4408, April 2006.

   [RFC5617]  Allman, E., Fenton, J., Delany, M., and J. Levine,
              "DomainKeys Identified Mail (DKIM) Author Domain Signing
              Practices (ADSP)", RFC 5617, August 2009.

   [RFC6376]  Crocker, D., Hansen, T., and M. Kucherawy, "DomainKeys

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              Identified Mail (DKIM) Signatures", RFC 6376,
              September 2011.

   [RFC6377]  Kucherawy, M., "DomainKeys Identified Mail (DKIM) and
              Mailing Lists", BCP 167, RFC 6377, September 2011.

   [RFC6449]  Falk, J., "Complaint Feedback Loop Operational
              Recommendations", RFC 6449, November 2011.

Authors' Addresses

   J.D. Falk
   Return Path
   100 Mathilda Street, Suite 100
   Sunnyvale, CA  94089


   M. Kucherawy (editor)
   128 King St., 2nd Floor
   San Francisco, CA  94107


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