The hacker collective Anonymous has made good on its threat to attack Sony, having launched a distributed denial-of-service attack on Wednesday afternoon.

The attack is revenge for the legal action taken against another hacker who modified a PlayStation 3. Sony Computer Entertainment America filed suit against George Hotz, also known as Geohot. Hotz had released a firmware modification that allowed a Sony PlayStation 3 to run other operating systems. Sony had removed that functionality some months before. The suit is still pending.

On Wednesday afternoon the site was down for about 20 minutes. The Anonymous IRC chat room #opsony there were remarks that seem as though Anonymous - a group with no formal leadership -was behind it. Some of the remarks on the chat were:

i'm launching a botnet with actual satellite links from Moscow to the direct expect it to be completely timed out in 30 minutes in which I will execute

stopped my loic [Low Orbit Ion Cannon] until we get a new target.

i just (sic) called sony and put the rep on hold and left the phone off hook

PlayStation Lifestyle reported that a splinter group of Anonymous was targeting Sony employees, and cited postings from a chat room that outlined names and addresses of people working at Sony. A look at the relevant chat room on Tuesday afternoon didn't show any links to personal documents. But it did have a link to the Operation Sony Facebook page.

Sony has hired an online security firm, Prolexic, to defend against the attacks. Prolexic's chief technology officer, Paul Sop, noted that most people think a DDoS is a simple flood of data. But they can often be much more sophisticated than that, sometimes involving only a few kilobits rather than megabytes worth of requests to a targeted machine.

The damage Anonymous does is real, he said. And they have a lot of smart people there. Generally speaking, he said Prolexic also has sophisticated tools that can tell when incoming traffic is deliberately randomized to mask that it is coming from a botnet - a group of compromised machines whose users may not even be aware they are being used in an attack.

Anonymous has a Facebook page that references April 16 as a day of some action, though it doesn't say what that might be.

A Sony spokesperson said the company is investigating the attacks, but would not give further details.