REPUTE Working Group N. Borenstein
Internet-Draft Mimecast
Intended status: Standards Track M. Kucherawy
Expires: July 16, 2012 Cloudmark
January 13, 2012
A Reputation Vocabulary for Email Identifiers
draft-ietf-repute-email-identifiers-02
Abstract
This document defines a vocabulary for describing assertions a
reputation service provider can make about email identifers, for use
with the application/reputon media type.
Status of this Memo
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This Internet-Draft will expire on July 16, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Definitions . . . . . . . . . . . . . . . . . . 3
2.1. Keywords . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Email Definitions . . . . . . . . . . . . . . . . . . . . . 3
2.3. Other Definitions . . . . . . . . . . . . . . . . . . . . . 3
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Assertions . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Vocabulary Extensions . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Registration of 'email-id' Reputation Application . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 6
Appendix B. Public Discussion . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This memo specifies a vocabulary for describing reputation of an
email identifier. A "vocabulary" in this context is defined in
[I-D.REPUTE-MODEL] and is used to describe assertions a reputation
service provider can make about email identifiers as well as meta-
data that can be included in such a reply beyond the base set
specified there.
2. Terminology and Definitions
This section defines terms used in the rest of the document.
2.1. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS].
2.2. Email Definitions
Commonly used definitions describing entities in the email
architecture are defined and discussed in [EMAIL-ARCH].
2.3. Other Definitions
Other terms of importance in this memo are defined in
[I-D.REPUTE-MODEL], the base memo in this document series.
3. Discussion
The expression of reputation about an email identifier requires
extensions of the base set defined in [I-D.REPUTE-MODEL]. This memo
defines and registers some common assertions about an entity found in
a piece of [MAIL].
3.1. Assertions
The "email-id" reputation application recognizes the following
assertions:
FRAUD: The subject identifier is associated with sending or handling
of fraudulent email, such as "phishing" (some good discussion on
this topic can be found in [IODEF-PHISHING])
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MALWARE: The subject identifier is associated with the sending or
handling of malware via email
SPAM: The subject identifier is associated with sending or handling
of unwanted bulk email
INVALID-RECIPIENTS: The subject identifier is associated with
delivery attempts to nonexistent recipients
For all assertions, the RATING scale is linear: A value of 0.0 means
there is no data to support the assertion, a value of 1.0 means all
accumulated data support the assertion, and the intervening values
have a linear relationship (i.e., a score of "x" is twice as strong
of an assertion as a value of "x/2").
3.2. Vocabulary Extensions
The "email-id" reputation application recognizes the following
OPTIONAL extensions to the basic vocabulary defined in
[I-D.REPUTE-MODEL]:
IDENTITY: A token indicating the source of the identifier; that is,
where the subject identifier was found in the message. This MUST
be one of:
DKIM: The signing domain, i.e. the value of the "d=" tag, found
on a valid [DKIM] signature in the message
IPV4: The IPv4 address of the client
IPV6: The IPv6 address of the client
RFC5321.MAILFROM: The RFC5321.MailFrom value of the envelope of a
message of the message (see [SMTP])
RFC5322.FROM: The RFC5322.From field of the message (see [MAIL])
SPF: The domain name portion of the identifier (RFC5321.MailFrom
or RFC5321.Helo) verified by [SPF])
RATE: A token that recommends an overall message acceptance rate for
the subject domain. This is expected to be a value tailored to
the requesting agent; for example, the reputation service would
use this to indicate that, based on the data reported by the
requesting agent, the service recommends a particular message
limit for that agent. The value is an unsigned decimal value.
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SOURCES: A token relating a count of the number of sources of data
that contributed to the reported reputation. This is in contrast
to the SAMPLE-SIZE parameter, which indicates the total number of
reports across all reporting sources.
A reply that does not contain the IDENTITY or SOURCES extensions is
making a non-specific statement about how the reputation returned was
developed. A client may use or ignore such a reply at its
discretion.
4. IANA Considerations
This memo presents one action for IANA, namely the registration of
the reputation application "email-id".
4.1. Registration of 'email-id' Reputation Application
This section registers the "email-id" reputation application, as per
the IANA Considerations section of [I-D.REPUTE-MODEL]. The
registration parameters are as folows:
o Application name: email-id
o Short description: Evaluates DNS domain names found in email
identifiers
o Defining document: [this memo]
o Status: current
o Application-specific query parameters:
subject: (current) specifies the subject of the reputation query;
in this case, it is the email identifier whose reputation is
requested
5. Security Considerations
This memo describes security considerations introduced by the
reputation application and vocabulary defined here.
[TBD]
6. References
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6.1. Normative References
[DKIM] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
"DomainKeys Identified Mail (DKIM) Signatures", RFC 6376,
September 2011.
[EMAIL-ARCH]
Crocker, D., "Internet Mail Architecture", RFC 5598,
July 2009.
[I-D.REPUTE-MODEL]
Borenstein, N. and M. Kucherawy, "A Model for Reputation
Interchange", I-D draft-ietf-repute-model, November 2011.
[KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[SPF] Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)
for Authorizing Use of Domains in E-Mail, Version 1",
RFC 4408, April 2006.
6.2. Informative References
[IODEF-PHISHING]
Cain, P. and D. Jevans, "Extensions to the IODEF-Document
Class for Reporting Phishing", RFC 5901, July 2010.
[MAIL] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
Appendix A. Acknowledgments
The authors wish to acknowledge the contributions of the following to
this specification: Scott Kitterman, John Levine, S. Moonesamy, Doug
Otis, and David F. Skoll.
Appendix B. Public Discussion
Public discussion of this suite of memos takes place on the
domainrep@ietf.org mailing list. See
https://www.ietf.org/mailman/listinfo/domainrep.
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Authors' Addresses
Nathaniel Borenstein
Mimecast
203 Crescent St., Suite 303
Waltham, MA 02453
USA
Phone: +1 781 996 5340
Email: nsb@guppylake.com
Murray S. Kucherawy
Cloudmark
128 King St., 2nd Floor
San Francisco, CA 94107
USA
Phone: +1 415 946 3800
Email: msk@cloudmark.com
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