Network Working Group N. Borenstein
Internet-Draft Mimecast
Intended status: Informational M. Kucherawy
Expires: May 3, 2012 Cloudmark
October 31, 2011
A Reputation Vocabulary for Email Identities
draft-kucherawy-reputation-vocab-identity-02
Abstract
This document defines a vocabulary for describing email identities
(typically authors or signers) with the application/reputon media
type.
Status of this Memo
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This Internet-Draft will expire on May 3, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Document Series . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology and Definitions . . . . . . . . . . . . . . . . . . 3
3.1. Keywords . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Email Definitions . . . . . . . . . . . . . . . . . . . . . 3
3.3. Other Definitions . . . . . . . . . . . . . . . . . . . . . 4
4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Assertions . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Vocabulary Extensions . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Registration of 'email-id' Reputation Application . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Informative References . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 6
Appendix B. Public Discussion . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
This memo defines a "vocabulary" for describing reputation of an
email identity. A "vocabulary" in this context is defined in
[RFCxxxx] and is used to describe assertions a reputation service
provider can make about email identities as well as meta-data that
can be included in such a reply beyond the base set specified there.
2. Document Series
This memo represents the media type registration, part of a series of
documents that define the overall service and introduce the initial
exemplary applications. The series is as follows:
1. RFCxxxx: A Model for Reputation Interchange
2. RFCxxxx+1: A Media Type for Reputation Information
3. RFCxxxx+2: Using UDP for Reputation Interchange
4. RFCxxxx+3: Using the DNS for Reputation Interchange
5. RFCxxxx+4: Using HTTP/XML for Reputation Interchange
6. RFCxxxx+5: A Reputation Vocabulary for Email Identity Reputation
(this memo)
7. RFCxxxx+6: A Reputation Vocabulary for Email Property Reputation
3. Terminology and Definitions
This section defines terms used in the rest of the document.
3.1. 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].
3.2. Email Definitions
Commonly used definitions describing entities in the email
architecture are defined and discussed in [EMAIL-ARCH].
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3.3. Other Definitions
Other terms of importance in this memo are defined in RFCxxxx, the
base memo in this document series.
4. Discussion
The expression of reputation about an email identity requires
extensions of the base set defined in [RFCxxxx]. This memo defines
and registers some common assertions about an entity found in a piece
of [MAIL].
4.1. Assertions
The "email-id" reputation application recognizes the following
assertions:
PERPETRATES-FRAUD: The subject identity is associated with
fraudulent email
SENDS-MALWARE: The subject identity is associated with the sending
or relaying of malware via email
SENDS-SPAM: The subject identity is associated with unwanted bulk
email
SENDS-TO-INVALID-RECIPIENTS: The subject 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").
4.2. Vocabulary Extensions
The "email-id" reputation application recognizes the following
extensions to the vocabulary defined in [RFCxxxx]:
IDENTITY: A token indicating the source of the identity; that is,
where the subject identity was found in the message. This MUST be
one of:
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DKIM: The signing domain, i.e. the value of the "d=" tag, found
on a valid [DKIM] signature in the message
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 identity verified by [SPF])
5. IANA Considerations
This memo presents one action for IANA, namely the registraton of the
reputation application "email-id".
5.1. Registration of 'email-id' Reputation Application
This section registers the "email-id" reputation application, as
defined in [RFCxxxx+1]. The registration parameters are as folows:
o Application name: email-id
o Short description: Evaluates DNS domain names found in email
identities
o Defining document: [this memo]
o Status: current
o Application-specific query parameters:
subject: (current) identifies the subject of the reputation
query; in this case, it is the email identity whose reputation
is requested
6. Security Considerations
This memo describes security considerations introduced by the media
type defined here.
6.1. General
This memo is part of a series introducing a reputation query and
response system (see Section 2). The Security Considerations
sections of the other memos should also be consulted.
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7. Informative 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.
[KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[MAIL] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
[SPF] Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)
for Authorizing Use of Domains in E-Mail, Version 1",
RFC 4408, April 2006.
Appendix A. Acknowledgments
The authors wish to acknowledge the contributions of the following to
this specification: 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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