mailing list archives
Re: WMFs blocked with MIME
From: Joachim Schipper <j.schipper () math uu nl>
Date: Fri, 6 Jan 2006 20:43:41 +0100
On Thu, Jan 05, 2006 at 01:35:36PM -0000, lsi wrote:
Preliminary testing reveals that emails containing WMF files can be
blocked by filtering for the MIME-encoded WMF header. This approach
works even if the file is called WORD.DOC. The string to check for
These 8 bytes appear as the first 8 bytes of a MIME-encoded WMF.
Thus, blocking all emails with those bytes in will block all emails
This technique can be used with common spam filters.
Regarding web-based WMFs, of the three browsers on this system, only
IE knows what to do with WMFs. Fortunately, I don't use IE. This
is, however, one more reason I can use to convince my customers to
That depends entirely on what 'MIME encoding' is. Base64? UUencode?
This is not to say that it is a bad point, and it can be useful as a
simplistic filter. But it is not more than that - even if you manage to
find patterns for all the above, there are numerous compression methods
that can be used.
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