The latest MyTob email worms have adopted fresh tactics in an attempt to trick victims. Instead of appearing in emails with virus-contaminated attachments, newer versions of the worm include a faked web link pointing to malicious code, mimicking tricks more commonly used in phishing scams.
Emails sent by the new versions of the MyTob worm masquerade as a seemingly legitimate email from the organisation's IT department or ISP, and suggest to users that a security problem has been found with their email account. Users are advised to click on the web link to confirm their account. References are made to the recipient's domain name and email address to give the message the smack of authenticity.
"By using this disguise, new versions of the MyTob worm attempt to lure the unwary into clicking on a dangerous web link," said Graham Cluley, senior technology consultant for Sophos. "This is a real headache for IT departments which often struggle to get their users to follow instructions. In this case, following the advice of the email would be a very bad idea."
Different variants of the MyTob worm currently account for 14 of the top 20 most commonly reported viruses to Sophos in the last seven days. Each only infects Windows PCs, as is the norm. The new versions of the MyTob worm contain a number of hidden messages. For instance, some claim the author's name is 'DiablO" and contain debug strings such as "[x] starting Hellbot::v3 beta 2'.
"All indications suggest that this isn't the last we will see of the MyTob worm. More versions seem certain to be released. It's imperative that everyone keeps their anti-virus protection up-to-date and practises safe computing," Cluley added.
Standard defence precautions against viral attacks apply in defending against MyTob: corporates should consider blocking executables at the gateway and update anti-virus signature definition files to detect the virus. Home users should also update anti-virus tools and resist the temptation to open suspicious-looking emails. ®