Posted by Virus Bulletin on Jun 19, 2010
Messages marked as 'not spam' from phony web mail accounts.
Connecticut spammer Boris Mizhen and several companies controlled by him have been sued by Microsoft for sending unwanted email to its customers and for gaming spam filters.
Mizhen has a long history as a spammer. For years he was listed in Spamhaus's ROKSO list and he was sued by Microsoft for sending spam to its web-based Hotmail service in 2003. That lawsuit ended in a settlement with Mizhen agreeing to pay Microsoft $2 million and to refrain from sending spam to Hotmail users.
In a new email campaign, however, Mizhen's companies once again targeted Hotmail users. An associate of Mizhen's claimed these messages weren't spam, explaining that many users had moved the messages from their junk folders to their inboxes. However, these user accounts are believed to have been specially created by Mizhen for this purpose.
Many spam filters base their filtering partially on user feedback. Using techniques such as Bayesian filtering, blacklisting and whitelisting, they attempt to learn from end users marking messages as 'spam' and 'not spam'. This case shows that such techniques can be abused by spammers - and developers of spam filters that use these techniques would be wise to keep this in mind when developing their products.