REPUTE Working Group N. Borenstein
Internet-Draft Mimecast
Intended status: Standards Track M. Kucherawy
Expires: October 8, 2012 Cloudmark
April 6, 2012
A Reputation Response Set for Email Identifiers
draft-ietf-repute-email-identifiers-03
Abstract
This document defines a response set for describing assertions a
reputation service provider can make about email identifers, for use
in generating reputons.
Status of this Memo
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This Internet-Draft will expire on October 8, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Definitions . . . . . . . . . . . . . . . . . . 3
2.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Email Definitions . . . . . . . . . . . . . . . . . . . . . 3
2.3. Other Definitions . . . . . . . . . . . . . . . . . . . . . 3
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Assertions . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Response Set Extensions . . . . . . . . . . . . . . . . . . 4
3.3. Query Extensions . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Registration of 'email-id' Reputation Application . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
Appendix B. Public Discussion . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This document specifies a response set for describing reputation of
an email identifier. A "response set" 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.
An atomic reputation response is called a "reputon", also defined in
that document.
2. Terminology and Definitions
This section defines terms used in the rest of the document.
2.1. Key Words
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 document are defined in
[I-D.REPUTE-MODEL], the base document for the reputation services
work.
3. Discussion
The expression of reputation about an email identifier requires
extensions of the base set defined in [I-D.REPUTE-MODEL]. This
document 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:
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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])
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. Response Set Extensions
The "email-id" reputation application recognizes the following
OPTIONAL extensions to the basic response set 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.HELO: The RFC5321.Helo value used by the (see [SMTP])
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])
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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 can use or ignore such a reply at its
discretion.
3.3. Query Extensions
A query within this application can include the OPTIONAL query
parameter "identity" to indicate which specific identity is of
interest to the query. Legal values are the same as those listed in
Section 3.2.
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 document]
o Status: current
o Subject: A string appropriate to the identifier of interest (see
Section 3.2 of this document)
o Application-specific query parameters:
identity: (current) as defined in Section 3.3 of this document
o Application-specific extensions:
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identity: (current) as defined in Section 3.2 of this document
5. Security Considerations
This section describes security considerations introduced by the
reputation application and response set extensions defined here.
[TBD]
6. References
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", draft-ietf-repute-model (work in progress),
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.
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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.
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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