Sex, drugs and obfuscation

The vast majority of spam attempts to disguise key words from filtering technology and slip them past anti-spam software at the email gateway, security experts have warned.

According to Sophos, these tricks can be as simple as deliberately misspelling a word or using a zero instead of the letter 'o', to much more sophisticated techniques that exploit the power of HTML email.

"Spammers have a dilemma," said Graham Cluley, senior technology consultant at Sophos.

"They want to sell certain products or include certain phrases in their spam emails, but they know that many people will have filters looking for those words and automatically junking them.

"For this reason they use obfuscation to try and disguise the words from the anti-spam software."

Sophos analysed a list of words based on the frequency with which they were used in spam email to determine which were most commonly disguised.

The company estimated that over 30 per cent of the spam it received contained URLs relating to healthcare advertisements, while over 20 per cent had offensive content within the message. Sexually explicit words made up 14 per cent of the top 50 words on the list.

"The list of words most commonly hidden by the spammers from anti-spam software reveals that most spam is about the old favourites: money, drugs and sex," explained Cluley.

"It is not only essential that people keep their anti-spam software up-to-date, but that they learn to rise up from the gutter of quick fixes and instant gratification, and resist their basic instincts to buy from spam mails.

"Spammers are criminals, plain and simple. If no-one responded to junk email, and didn't buy products sold in this way, spam would be as extinct as the dinosaurs."

The list of words that spammers most commonly disguise compiled by Sophos can be found here.