Fighting malware and spam

DKIM usage shows significant growth

US banks urged to use authentication method

In a report on its website, Internet giant Cisco states it has been seeing almost 700,000 non-spam messages that contain valid DKIM signatures per week - a number that has almost tripled since a year ago.

DKIM (DomainKeys Identified Mail) is an authentication method where the sending mail server adds a signature to the email header that can be used by the recipient to verify that the message has not been tampered with along the way. While not an anti-spam measure in itself (it is possible for spammers to sign their own messages) a DKIM signature combined with a trust relationship between sender and recipient can significantly reduce false positives.

The method is especially useful for senders whose domains are regularly targeted by phishers: by signing all their outgoing email, they implicitly tell recipients they can discard all email claiming to come from the domain that contains no, or an invalid, DKIM signature. Not surprisingly therefore, BITS, a division of The Financial Services Roundtable, has published a paper (PDF) in which it urges its members, most of which are US banks, to use DKIM and SPF for all email they send.

More information on mail authentication with DKIM can be found in two articles published in Virus Bulletin magazine recently (1, 2) (available to Virus Bulletin subscribers - subscription information can be found here).

29 June 2009

Tags: bits, dkim, false positive, phishing, spam, spf.    del.icio.us   digg this

1 comment

What is definitely scary for this is that we have also observed a dramatic increase in the number of dkim signed spam, especially with cheap domains available (.cn at around 2$ per month, to register almost anonymously)

by marc, 02 July 2009, 19:39

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