Using signature headers to determine if an email has been forged - Revision history

Jessek: /* Sender Policy Framework */ Formatting oops

2007-04-29T18:32:58Z

‎Sender Policy Framework: Formatting oops

Jessek: Added SPF records

2007-04-29T18:32:09Z

Added SPF records

Jessek: Fleshed out slightly

2007-04-29T18:26:29Z

Fleshed out slightly

Jessek: /* DomainKeys Identified Mail */ - Fixed link

2007-04-29T18:23:43Z

‎DomainKeys Identified Mail: - Fixed link

Jessek: /* Domain Key Signatures */

2007-04-29T18:23:03Z

‎Domain Key Signatures

Jessek: /* Signed mail */ - Quick notes on PGP signed and/or encrypted messages

2007-04-29T18:01:16Z

‎Signed mail: - Quick notes on PGP signed and/or encrypted messages

Jessek: Initial stub

2007-04-28T16:58:25Z

Initial stub

New page

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== Domain Key Signatures ==

These headers, included by the mail server, provide a signature of each message. See [[Gmail Header Format]]. The public keys are distributed via [[Domain Name System|DNS]].

== Signed mail ==

Some other programs can be used by the sender to sign an email message. Programs such as [[PGP]], [[GnuPG]].

== See Also ==
* [[Using message id headers to determine if an email has been forged]]

[[Category:Howtos]]

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 == Sender Policy Framework ==
 {{main|Sender Policy Framework}}
-Sender Policy Framework, or SPF records, can be used to enumerate which hosts are allowed to send mail for that domain. If a message purports to be from ''example.com'' but came from an IP address that is not authorized, under SPF, to send mail for that domain, it has been forged. As an example, let's say we have an email purporting to be from <tt>example.com</tt>. The message was sent by <tt>lexluthor@mit.edu<.tt> using the IP address <tt>4.61.91.6</tt>. An investigator can query the DNS records from that domain, in this case <tt>mit.edu</tt> to see the SPF senders.
+Sender Policy Framework, or SPF records, can be used to enumerate which hosts are allowed to send mail for that domain. If a message purports to be from ''example.com'' but came from an IP address that is not authorized, under SPF, to send mail for that domain, it has been forged. As an example, let's say we have an email purporting to be from <tt>lexluthor@mit.edu</tt> using the IP address <tt>4.61.91.6</tt>. An investigator can query the DNS records from that domain, in this case <tt>mit.edu</tt> to see the SPF senders.
 <pre>$ host -t txt mit.edu

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 {{Expand}}
 Email signatures, designed for authentication, non-repudiation, and spam control, can also be used to determine if an email has been forged. In the most common case, the forger copies headers from an existing email message to a new one. He could also attempt to change the content of a signed message. Regardless, the signature no longer corresponds to the message and it can be shown that the message is not authentic.
 == DomainKeys Identified Mail ==

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 {{Expand}}
+Email signatures, designed for authentication, non-repudiation, and spam control, can also be used to determine if an email has been forged. In the most common case, the forger copies headers from an existing email message to a new one. He could also attempt to change the content of a signed message. Regardless, the signature no longer corresponds to the message and it can be shown that the message is not authentic.
 == DomainKeys Identified Mail ==
 {{main|DomainKeys Identified Mail}}
 These headers, included by the mail server, provide a signature of each message. See [[Gmail Header Format]]. The public keys are distributed via [[Domain Name System|DNS]].

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 == DomainKeys Identified Mail ==
-{main|DomainKeys Identified Mail}
+{{main|DomainKeys Identified Mail}}
 == Domain Key Signatures ==

← Older revision		Revision as of 18:01, 29 April 2007
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	Some other programs can be used by the sender to sign an email message. Programs such as [[PGP]], [[GnuPG]].		Some other programs can be used by the sender to sign an email message. Programs such as [[PGP]], [[GnuPG]].
		+
		+	=== PGP Messages ===
		+
		+	Messages sent using PGP, or its free equivalents such as GnuPG, have the signature in the message body itself. Each message can be signed, encrypted, or both. Encrypted messages begin with the header
		+	<pre>-----BEGIN PGP MESSAGE-----</pre> followed by some optional headers. The optional headers may include the character set of the decoded message, the program and version that created the message, and an optional comment. The end of the message is noted with <pre>-----END PGP MESSAGE-----</pre> Between these two lines are a series of ASCII characters that represent the encrypted or signed message.
		+
		+	A signed message has the header <pre>-----BEGIN PGP SIGNATURE-----</pre> at the ''end'' of the signed message followed by the same optional headers as encrypted messages. The signature is usually three lines of ASCII characters.

	== See Also ==		== See Also ==