In early July of 2006 there was a prominent stream of spam messages that simply quoted three random lines of the book 'the hobbit', with a subject header of 6 random letters. The popular belief is that this was a 'script kiddie' who had got hold of spam suite and was inept in it's use. This belief was reinforced shortly after when the same messages began appearing with an image overlaid, a popular spammer trick(The seemingly innocent words allow the message to bypass filters but all that is displayed on opening the message is the picture).
It's nice to put seemingly random and pointless messages down to inept practice on the part of the spammer, but my personal belief is this is not the case. To me this seems to look like a deliberate attempt to corrupt the improving Bayesian Filter technology. Bayesian filters work by assigning a spam score to words that are found in spam e-mails. The more regularly they appear in a spam message, the higher the spam score and the more likely a message contianing those words is to be marked as spam.
Given that piece of knowledge, imagine the implications of a concerted campaign of spammed messages that contains a short message of commonly used words. The 'spam score' of these words is elevated, the effectiveness of the bayesian filter is diminished and when the real spam message is sent through the defenses are lowered, or indeed have been removed having provided too many false positives.
The obvious clue to me is in the way these messages are sent. Firstly the title is randomised. Many Bayesian filters treat nonsense as 'high spam' score. Furthermore title text is usually given a higher priority than body text. Thus a nonsense title may be enough to get a message banned by itself, and combined with a common spammer trick such as the picture overlay, it seems the spammer wanted these messages to be caught.
As more people come to rely on Bayesian filtering, this will become a more and more serious problem. We already know spammers are prepared to send out millions of messages just to get one sale. Now it appears that they are also prepared to make multiple mailings to those millions of addresses just to soften up anti-spam defenses for their one commercial mailing.
