spam from the list

Glyn Grinstead glyn at uk.freebsd.org
Wed Jun 4 18:54:00 BST 2003


On Wed, Jun 04, 2003 at 05:53:52PM +0100, Pete French wrote:
> actually I hadnt heard of spamassasssin until today - I guess its siimilar
> to bogofilter, which we just use to tag headers. then our users can filter
> how they want. its been an interesting discussion today actually - the
> comments about one persons spam being another persons message are particularly
> relevent to us. in fact I am beginning to think that what we really want is
> to set up the filitering on a per-user basis. Some of our users are on
> mailing lists where the contents of the messages would probably have a very
> high crossover with a lot of the more salacious spam doing the rounds.

I don't have any experience of bogofilter, but I started using Spam
Assassin at the very beginning of April and I've been very impressed 
with it. So far it's caught 864 spams with no false positives and only a 
few missed - and that's without Bayesian filtering until a week or so ago.

The main selling point with Spam Assassin for me is that it doesn't rely on
a single test. As well as keyword analysis it also uses black hole look 
ups, Razor lookups (database of known spam messages), Bayesian analysis
and header and body analysis (e.g. forged received lines, low ratio of text
to image area etc.). 

All the scores seem well tuned, so different black lists are weighted 
differently (presumably according to how well the results are trusted),
and there are a multitude of trivial tests (using red text will get you
one tenth of a point) that can be the deciding factor on a borderline 
message. 

You can use Spam Assassin in a number of ways. A typical way is to let 
it add a header to all messages to indicate the level of spam. After 
a set point the email is normally replaced with a Spam Assassin message 
giving a preview of the message and an explanation as to why it was 
considered to be spam, with the original message as a MIME attachment.

If you want you can just add the header and leave the message unaltered
for the user to take whatever action they want to, but then you miss 
the detailed explanations such as:

MLM                (0.8 points)  BODY: Multi Level Marketing mentioned
NOT_MLM            (2.9 points)  BODY: Apparently, NOT Multi Level Marketing

Of course, since installing Spam Assassin I've ended up spending far
more time looking at my spam than ever before, but I've now written a 
script to do that for me as well (it sends me a short summary every day)
so hopefully I can, at last, get back to having a usable mailbox again.

Glyn.




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