The latest version of the Bagle mass mailer worm attempts to threaten potential victims by posing as a lawsuit against the recipient.

Bagle-DO worm spreads in emails featuring subject lines such as "Pay your debts before we come to you", "Call to your lawyer immidiately", "Lawsuit against you" and "We wait your response". Users are prompted to open an infectious attachment (called lawsuit.exe, explanation.exe or documents.exe) which installs malware on compromised PCs. The worm then executes routines which seek to infect other computers via email or P2P networks posing as nude pictures of actress Kate Beckinsale, or erotic photographs of celebrity hotel heiress Paris Hilton and pop strumpet Britney Spears.

The body text of infected messages vary, but all claim to refer to supposedly pending legal action against the recipient. Examples include emails that claims the recipient's firm sent an unsolicited commercial fax without permission. Another talks about a car maintenance job that went disastrously wrong, resulting in a fire.

Although the legal threat angle is a slight spin on well-established social engineering tricks, the tactic has proved to be largely ineffective. Bagle-DO is spreading, but only to a limited extent. Anti-virus firms rate it as a low-risk nuisance. ®