Thursday's denial-of-service attack that knocked Twitter offline for a few hours and affected Facebook, LiveJournal, and Google Sites and Blogger wasn't your average attack.

Typically, someone who has a bone to pick with a specific Web site will round up some hijacked PCs and use them to try to shut the site down. In this case, whoever was responsible was trying to block access to a specific user's accounts and not the sites themselves.

Denial-of-service attacks aren't always straight forwa...

The denial of service attacks against Web sites in the U.S. and South Korea that started last weekend may have stopped for now, but code on the infected bots was set to wipe data on Friday, security experts said.

There were no immediate reports of any of the compromised PCs in the botnet having files deleted, but that doesn't mean it wasn't happening or won't in the future, said Gerry Egan, a product manager in Symantec's Security Technology Response group.

There are only about 50,000 infe...