* Another technique spammers use to get through filters
The nasty people who flood our e-mail with unwanted advertising have been using increasingly deceptive means to elude spam-filtering software, most of which runs on the same principle as signature-based anti-virus software or misuse-detection intrusion detection systems. The defensive products rely on intelligence from the field to identify known patterns of subject lines and content to screen spam from their users.
A simple technique that spammers have used recently is to find synonyms for the keywords that are blocking their junk; thus they may use the chemical or generic name of various drugs instead of the brand name. To avoid blockage of this message by readers’ anti-spam tools, I won’t give specific examples here. The names are also spelled wrong in a wide range of ways – not by mistake, one can be sure. Anti-spam products may have to extend their search strings to include likely misspellings of key words.
Some spammers are shifting to almost exclusively HTML e-mail with embedded images that represent their text. Thus instead of being able to scan for the keywords that characterize so much of this repetitive garbage, the anti-spam tools are faced with bland HTML for a couple of links and an unscannable bit-image that contains no machine-readable text.
Here, for example, is the source of an unwanted advertisement for a drug (by the way, you’d surely have to be mad to trust a drug from an organization that sends spam):
http://www.ABCDE.com/host/default.asp?ID=omni“>http://FGHIJ.com/pics/gv1.gif” height=”270″ width=”405″>
