While the Code Red worm grabs headlines and alarms Internet users around the world, SirCam has been quietly wreaking havoc in the background, infecting computers and sending out potentially sensitive files.
The virus is responsible for secret documents being leaked from the administration of Ukrainian President Leonid Kuchma this week to the ForUm news Web site, site operators said.
A computer at the FBI's National Infrastructure Protection Centre became infected with the virus late last month and sent some private, though not sensitive or classified, FBI documents out in emails as a result, officials said.
The virus, which has been rated high risk by most antivirus vendors, was the top-ranking virus in July, with over 38 percent of the share of virus infections, according to antivirus software company Central Command.
SirCam has turned out to be both nastier and longer-lived than experts had expected, partly because its appearance changes as it spreads, said Andy Faris, president of MessageLabs Americas.
"It's a much more serious outbreak than most vendors originally forecast," said Faris. "It's the single most prolific virus in our customer base," of about 3,000 customers and 500,000 users.
Experts first detected Sircam in July and saw its first peak on July 25. Unlike most viruses that die off after they peak, the number of computers infected by Sircam rose again to spike anew on Tuesday, according to email security outsourcer MessageLabs Americas, raising the possibility that it could jump again.
