The U.S. Federal Bureau of Investigation is warning computer users not to open a widely circulating e-mail that falsely claims
to have been sent by U.S. authorities. The e-mail attempts to trick users into installing a variant of the Sober worm by telling
them that they have been spotted on "illegal Websites," and asking them to click on an attached "list of questions."
"These e-mails did not come from the FBI," the FBI said in a Tuesday statement posted at http://www.fbi.gov/pressrel/pressrel05/emailscheme112205.htm.
"Recipients of this or similar solicitations should know that the FBI does not engage in the practice of sending unsolicited
e-mails to the public in this manner."
This latest worm now accounts for more than 65 percent of all malicious software being reported to antivirus vendor Sophos (Profile, Products, Articles) PLC, and makes up about one in every 74 e-mail messages being sent on the Internet, said Graham Cluley, a senior technology
consultant with Sophos. "It's quite a significant event," he said. "I'm not sure that it's necessarily going to last, but
at the moment it's well ahead of any other virus."
Once launched, Sober scans the user's hard drive for e-mail addresses and sends the bogus e-mail to new recipients. After
that, it awaits further instructions from its creator, effectively turning the infected system into a remote-controlled zombie
computer that could be used for further spamming or computer attacks.
Sometimes the worm pretends to come from the U.S. Central Intelligence Agency (CIA) or German police, Cluley said.
Variations of the Sober worm have been circulating for about two years now, and their code is similar enough that they are
all thought to have been written by one person, or perhaps a small group of people, Cluley said.
By mentioning U.S. law enforcement, the worm writers have made it more likely that users will inadvertently launch malicious
code, but they may also be goading the FBI and the CIA, Cluley said. "It seems a bizarre thing for the virus writer to do,
to pick a fight with the FBI and CIA in this way."
The FBI is taking the matter "seriously," and is investigating, the agency's statement said.