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The "Virus Bounce Ruleset" is a SpamAssassin ruleset to catch "backscatter".

Wiki MarkupBackscatter is mail you didn't ask to receive, generated by legitimate, non-spam-sending systems in response to spam. Here are some examples, \[http://www.spamresource.com/2007/02/backscatter-what-is-it-how-do-i-stop-it.html courtesy of Al Iverson\]:

• Misdirected "undeliverable email" bounce messages from spam runs, from mail servers who "accept then bounce" instead of rejecting mail during the SMTP transaction.
• Misdirected virus/worm "OMG your mail was infected!" email notifications from virus scanners.
• Misdirected "please confirm your subscription" requests from mailing lists that allow email-based signup requests.
• Out of office or vacation autoreplies and autoresponders.
• Challenge requests from "Challenge/Response" anti-spam software. Maybe C/R software works great for you, but it generates significant backscatter to people you don't know.
  

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If you are using SA 3.1.x, you can install the ruleset as follows:

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1. Download \[http://svn.apache.org/viewvc/spamassassin/rules/trunk/sandbox/jm/20_vbounce.cf?revision=482200&pathrev=482207 20_vbounce.cf\] and \[http://taint.org/x/2007/VBounce.pm VBounce.pm\]. \\
   

2. Save both files to your /etc/mail/spamassassin directory.

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If upgrading from 3.1.x to 3.2.0, you need to delete VBounce.pm and 20_vbounce.cf from /etc/mail/spamassassin, so that it doesn't clash with the released version.

Further Steps

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If you're using Postfix, and volumes of backscatter at your mailserver are very high, you can also block incoming backscatter during the SMTP transaction. \[http://taint.org/2007/05/30/164456a.html This blog post\] describes how to do it.

What About My Own Bounces?

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