Secret Code Lurks in Sober Variant

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Security vendors warn infected computers may attack in January.


Security vendors have discovered a variant of the Sober worm that they say is programmed to download an unknown piece of code from various Internet addresses early in January, potentially launching a barrage of digital traffic.

Threat, Targets Identified

Security firm iDefense said it broke the encrypted code in a Sober variant discovered in November and found that it is designed to download the unknown code from various Web addresses on January 5, 2006. Millions of "zombie" computers may already be infected with the variant, the company said. The date coincides with the 87th anniversary of the founding of the Nazi Party. The release of worms has been tied to political events in the past, iDefense noted, in a kind of "hactivisim" designed to distribute propaganda.

Mikko Hypponen, chief research officer for F-Secure, said the worm will try to download the mystery code from 14 URLs at four different ISPs. F-Secure has contacted those ISPs, all in Austria and Germany, and requested that the addresses be blocked before the trigger date. At least one of them has responded positively, he said.

The writer of the worm doesn't seem interested in money, Hypponen said. The code may end up downloading propaganda to a user's computer, or it may distribute further malicious code which then sends out messages to other computers, clogging the Internet.

Sober Tactics

The Sober variant synchronizes itself with an online atomic clock to coordinate the attack, and the URLs many be scheduled to go online just before the code is activated in users' computers, Hypponen said. The addresses, which were obtained by cracking the code, do not currently work, he said.

Many of the Sober variants have spread by appearing to be e-mail from the FBI or CIA or other law enforcement agencies. After malicious code in an attachment is executed, the worm spreads by sending itself to other e-mail addresses contained on the infected PC.

The Sober worm has been the most prevalent nuisance of the year. It has appeared in more than 30 variants since it was first found in October 2003, iDefense said. It's believed to have been created in Germany, and also appears in the German language.