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The Internet was quiet as the clock ticked past the scheduled start time for a massive, coordinated action by Microsoft Windows machines infected with the Sobig.F virus.

Beginning on Friday, antivirus companies warned of the possible danger posed by an unknown file that Sobig machines were programmed to download and run beginning at 3 p.m. EST.

Using atomic clocks associated with universities and governments around the world to coordinate their actions, the Sobig machines were scheduled to search a list of 20 Sobig.F servers that were individually hacked by the virus author and supplied with instructions to download and run a special file.

Security experts warned about the possibility of denial of service attacks, as thousands of Sobig-infected machines were all pointed to a single Web site.

Virus authors could also instruct the infected machines to download a Trojan horse program, giving the author a back door into the infected system for future use, experts said.

Preventative Measures

The CERT Coordination Centers in the United States and Europe and the U.S. Federal Bureau of Investigation were informed of the threat and worked to notify the Internet service providers that hosted the machines named by Sobig so they could be taken offline, according to Mikko Hyppönen, director of antivirus research at F-Secure in Helsinki.

That effort appears to have been successful.

"It's pretty quiet," said Johannes Ullrich, CTO of the SANS Institute's Internet Storm Center shortly after the mass action was scheduled to begin.

Ullrich did not notice any change in Internet traffic around the time Sobig was scheduled to download its instructions.

Server Stories

There were conflicting reports Friday about whether all or just some of the Sobig servers were taken offline.

Network Associates said that none of the 20 servers was online, according to Jimmy Kuo, a research fellow at NAI.

Internet Security Systems reported that one of the 20 was still online at 3 p.m., but that no new instructions had been placed on the machine by the virus writer, according to Dan Ingevaldson, engineering manager at ISS.

The last Sobig server stopped responding shortly after 3 p.m., he said.

With few or none of the 20 servers accessible, Sobig machines were unable to download any instructions, experts agreed.

Lessons Learned

In addition, Internet backbone providers may have been asked to drop any traffic destined for those addresses, similar to steps taken to prevent a scheduled denial of service attack against the White House that was programmed into the Code Red worm, Kuo said.

Such a move is standard procedure when Internet abuse and crime is tied to a specific machine or machines, according to Ingevaldson.

In any case, once authorities began shutting down the IP addresses of machines used by the worm, it is doubtful that the author would have risked uploading new instructions to one of those machines, Kuo said.

"My guess is the author saw how big and fast Sobig propagated and didn't want to go any further," Ingevaldson said.

Regardless of the outcome of the Sobig attack Friday, writers of future worms may well learn from the successes of Sobig.F and incorporate that knowledge into future viruses, he said.

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