What I don't understand is how can a linux mailing list (a list DEDICATED to
linux) can be effected by a WINDOWS virus.

First, any virus sent to the list should be ineffective, because everyone should
be running linux right?

Second, a virus should not be sent to the list because of the first point.

How about a procmail receipe like this:

:0B
* ^X-Mailer: Microsoft.*
{
  :0
  /dev/null
}

-- 
Bob Tanner <tanner at real-time.com>       | Phone : (952)943-8700
http://www.mn-linux.org                 | Fax   : (952)943-8500
Key fingerprint =  6C E9 51 4F D5 3E 4C 66 62 A9 10 E5 35 85 39 D9