Microsoft said it had yet to be affected by a Mydoom-B, worm-induced distributed denial of service (DDoS) attack, which antivirus software companies predicted would be fairly easy for the software company to fend off.
Unlike The SCO Group's site, which has been assailed by a denial of service (DOS) attack from Mydoom-A worm since Sunday and continues to fight off attacks from both the A and B variant of the Mydoom worm, a Microsoft spokeswoman in the U.K. said that "everything on the Microsoft site seems to be working fine."
The Mydoom-B worm is similar to the Mydoom-A worm but contains an added DOS attack against Microsoft's website and a feature that blocks access to anti-virus websites on infected machines.
According to the code in the worm, the DOS attacks against SCO, a Unix vendor based in Lindon, Utah, are scheduled to continue through 12 February.
Microsoft has classified the second variant of the worm as a moderate threat and said it has been well prepared for the DDOS attack, which it expected to begin on Sunday, the spokeswoman said.
"Although Microsoft is unable to discuss the specific remedies it is taking to prevent the reported DDOS attack, we are doing everything we can to ensure that Microsoft properties remain fully available to our customers," the company said on its website. "Microsoft is aggressively working with our Virus Information Alliance partners to help protect customers from this outbreak."
The Mydoom-B worm is generally considered by leading anti-virus software companies and e-mail security firms to be less effective than Mydoom-A at propagating itself and causing widespread damage to computer systems. London-based Sophos PLC on Tuesday said it has received very few reports of actual Mydoom-B infected computers.
The small number of reports of Mydoom-B suggests that the attack on Microsoft will fail, according to Graham Cluley, senior technology consultant at Sophos.
"There was only about a day's separation between Mydoom-A and Mydoom-B, so it's my guess that the real target of the virus writer was SCO while an attack against Microsoft was something of an afterthought," Cluley said. "When it comes to being able to spread itself, Mydoom-B didn't get as lucky as Mydoom-A, which still poses a significant threat."
Although both SCO and Microsoft are offering rewards of US$250,000 each for information leading to the arrest and conviction of the person or persons responsible for creating and releasing both versions of the Mydoom worm, Cluley sees little chance the money will lead to an arrest.
"It is a long shot, to be honest, but bounties or rewards don't do any harm either and may actually discourage virus writers in the future as it shows companies are serious about catching those responsible," Cluley said. "If virus writers know there is a strong cash incentive for someone to grass them up, they may think twice about unleashing a virus."