That means they could be used to launch a distributed denial-of-service attack on a victim's computer.

CNN: New denial-of-service attack tool uses chat programs

The distributed denial-of-service attack failed to crash those payment networks, but David says Anonymous did manage to poke around their back-end computer systems.

FORBES: Magazine Article

Spamhaus accused Cyberbunker, a Dutch Web-hosting company, of coordinating the so-called distributed denial-of-service attack against it, according to a report by the British Broadcasting Corp.

WSJ: Cyberattack on Spam Fighter Said to Be Over

Rouland points out that ISS Tuesday discovered a chat room called "IP Victims" on Yahoo that is being used for the exchange of IP addresses of machines compromised by the Trojan horse Back Orifice and an older distributed denial-of-service attack tool called Sub Seven.

CNN: New denial-of-service attack tool uses chat programs

In a tweet on its Twitter feed, MTGox said it was fighting off a distributed denial-of-service (DDoS) attack, which involves a site being bombarded with huge amounts of data.

BBC: Wall Street sign

One of the Internet Protocol (IP) addresses used to break into Nonghyup's system was the same as one used in March for a distributed denial-of-service (DDoS) attack that originated in North Korea, they added.

BBC: North Korea 'behind South Korean bank cyber hack'

This so-called Distributed Denial of Service (DDoS) attack relies on having enough users, voluntary or not, to flood a site with so much traffic that it gets shunted offline.

FORBES: Click 'n Hit: How Supporters Of Anonymous?Are Making It Easier To Cripple Websites