[Spambayes] Have you ever....?

[Skip Montanaro]

    John> Ever notice the random set of characters at the end of most spam
    John> messages these days?  Does anyone know what they are for?  Perhaps
    John> these characters might be of use.  Are they some sort of checksum
    John> or signature?

They are probably there to try and foil systems which use checksums to try
and detect spam.  Large email providers like AOL or MSN can probably very
quickly conclude an email is spam if they see the same checksum a handful of
times (100? 1000? 10000?).  The more messages which arrive with the same
checksum, the more likely they are to be spam.  The random drivel is an
attempt to work around these sorts of systems.

There are distributed systems, like Razor, which rely on checksums as well.
For an example of a script which tries to compute a "loose" checksum (and
may fail in the case you mentioned), look at the loosecksum.py script in the
spambayes CVS repository.

Skip