|After blocking donations to WikiLeaks, MasterCard's Web site was hacked|
Twitter and Facebook are at the center of a storm of controversy over involvement with WikiLeaks, which has released an unprecedented, huge cache of confidential diplomatic documents.
Anonymous hackers have targeted MasterCard, Visa and PayPal, all of which have closed their WikiLeaks' accounts, thus blocking donations to the group. A hacking campaign called Operation Payback organized by a group called Anonymous has used Facebook and Twitter to single out targets and publicize successful hacks.
In response, Facebook closed one of the group's pages. Twitter later closed its Operation Payback account after the group posted a link to a file that identified thousands of credit card numbers, according to a report in the New York Times.
WikiLeaks's Twitter account is still active. It is the group's main channel for communicating with supporters and the media. WikiLeaks also still has an official Facebook page.