New MyDoom worm uses search engines to spread

Internet users are being threatened by yet another variant of the MyDoom mass mailing worm, which is spreading in part by using e-mail addresses found through popular search engines, security experts warned.

The new variant was first spotted late Wednesday and reports from computer users suggest the worm is already circling the globe, according to Graham Cluley, senior technology consultant at Sophos.

The worm proliferates by e-mailing itself through its own SMTP engine, according to Sophos. When it infects a computer it scans the hard disk for e-mail addresses and then takes the domains of the addresses it finds and queries search engines such as Google, Yahoo and Lycos looking for similar addresses, Cluley said.

If it finds the address JohnDoe@yahoo.com, for instance, it will use a search engine to look for other addresses at the yahoo.com domain to send itself to, Cluley explained.

A similar MyDoom variant appeared last July and managed to slow some search engines as it flooded them with queries. Cluley said he doubts the new variant will have the same effect since this outbreak is not as severe. Additionally, search engines have taken measures to prevent being crippled by the worm again, Cluley said.

The latest worm was created by repackaging an older MyDoom variant in an encrypted "wrapper" so that anti-virus software could not recognize it, Cluley said. The method is just one of the clever ways hackers use to hide their attacks and anti-virus firms should be aware of the ruse, he added.

Internet users should make sure their antivirus software is up to date to avoid infection.

The IDG News Service is a Network World affiliate.