An expected Internet attack spurred by the Sobig worm fizzled out on Friday, apparently due to the coordinated efforts of security experts, the FBI and Microsoft.

Researchers at two security firms warned that a potentially massive attack was scheduled to be launched Friday when computers infected with the Sobig.F worm would be forced to download and run a mysterious program at 19:00 UTC (3 p.m. EDT).

At 3 p.m., the virus directed a few infected computers to a pornography website but that site shortly collapsed under a flood of network traffic.

"Of the 20 servers identified to be used for the attack, 16 are down, three are not responding and one is responding and directing traffic to a porn site,'' the antivirus firm Symantec said in a statement...