A hacker who was charged with using approximately 20,000 virus-infected computers to attack online auction firm eBay in 2003 has pleaded guilty, the United States Attorney's office said on Wednesday.

The hacker, Anthony Scott Clark, 21, of U.S. state Oregon, helped to launch distributed Denial of Service attacks on the Internet against eBay, according to prosecutors.

Clark and his accomplices used a worm program called "bot" that exploited a vulnerability in the Windows Operating System. The "bots" were then directed to an Internet chat server, where they connected, logged in, and waited for instructions.

"Mr. Clark personally commanded the 'bots' to launch DDOS attacks on the name server for eBay.com," and, "as a result of these commands, Mr. Clark intentionally impaired the infected computers and eBay.com," the Attorney's office said in a statement.

Clark admitted to the charges at a federal court in San Jose, California, on Tuesday afternoon. Prosecutors said Clark faces a potential sentence of up to 10 years in prison, a fine of 250,000 U.S. dollars, and three years supervised release.

But the arrest is unlikely to make a dent in the number of botnets or their usage, security experts warned. Attacks using botnets are difficult to track, because they are usually cross-border attacks and anonymous.

"It is difficult to tell who's pushing the buttons," said Joseph Telafici, director of operations for the Anti Virus Emergency Response Team at anti-virus software maker McAfee.

"Botnets are the biggest source of cash flow in organized Net crime as they are used to drop adware into user computers, for spam relays, data theft, and to launch DDOS attacks," Telafici told Red Herring, a well-known technology magazine.

Source: Xinhua