It was initially thought that Anonymous was behind the attack, because The Pirate Bay openly criticized Anonymous' DDoS attacks against Virgin Media, a UK ISP that blocked access to the popular torrent site.
But the hacktivist group denied it, and The Pirate Bay confirmed that they were not on its Facebook page.
"We may not agree with Anonymous in everything, but we both want the internet to be open and free," they pointed out.
Then yesterday, a hacker that goes by the handle "Anonymous Saint", or "AnonNyre", took credit for the The Pirate Bay takedown:
The hacker explained the reason for the attack in a Pastebin post:
You must be wondering why did I attacked The Pirate Bay.. I am Nyre. I am highly against Anonymous. I do not support Anonymous anymore. I sometimes help the feds. The Pirate Bay was a press-release website for Anonymous, then I had a idea, why not take it down? Why not make it impossible for Anonymous?
After having initially stated that he(?) will try to keep The Pirate Bay offline for a week, the hacker seems to have changed his mind - that is, if he's actually the one behind the attack.
It's difficult to say whether the attack against TPB and WikiLeaks had the same source, and AnonNyre doesn't mention WikiLeaks at all.
Whoever is behind the attacks, they must have a sizable botnet at their disposal. The Pirate Bay administrators said that they have their suspicions, but haven't revealed them yet.