Hackers today shut down MasterCard Worldwide's website and disrupted cardholders' payments in retaliation for the Purchase, N.Y.-based card association cutting off donations to WikiLeaks.

Hackers from around the world launched a coordinated "denial of service" attack on MasterCard at the height of the holiday spending season. MasterCard is the world's second-largest card association behind Visa.

MasterCard acknowledged the effects of the cyber attack in a terse four-line statement:

Please be advised that MasterCard SecureCode Support has detected a service disruption to the MasterCard Directory Server. The Directory Server service has been failed over to a secondary site however customers may still be experiencing intermittent connectivity issues. More information on the estimated time of recovery will be shared in due course.

MasterCard, which stopped processing payments to WikiLeaks, initially said the cyber attack had no impact on people's ability to use their cards, but unnamed processors reported they were unable to approve MasterCard transactions. Officials of Atlanta-based First Data Corp. said the company did not experience any problems processing MasterCard transactions.

Adil Moussa, an analyst with Aite Group LLC, was talking with this reporter when he attempted use his MasterCard. "My card has been declined," Moussa said.
 
Attack prompted by WikiLeaks controversy

The attack on MasterCard.com comes one day after the anonymous hacker collective Operation: Payback took down the website of the Swiss bank PostFinance. Both attacks, along with a recent campaign against PayPal, are prompted by outrage over the organizations' refusal to process donation transactions to the group WikiLeaks.

MasterCard announced Monday that it was shutting down payments to WikiLeaks.

"MasterCard is taking action to ensure that WikiLeaks can no longer accept MasterCard-branded products," a spokesperson said then.

WikiLeaks, the non-profit publishing company that publishes anonymously-submitted private documents and leaks, has been at the center of global controversy since it began publishing more than 250,000 U.S. State Department diplomatic cables in late November.

Several businesses that interact with WikiLeaks have pulled their services — including Amazon, MasterCard, Visa and Paypal, among others — and the online vigilante group known as Anonymous announced it is "declaring war" on those companies, asking supporters to stage attacks against them.

Operation: Payback, the Anonymous party behind the current siege of MasterCard, is using its Twitter feed to rally its troops. "Current Target: www.mastercard.com | Grab your weapons here," read several recent tweets, followed by a link to the tools necessary to take part in the attack.

UPDATE: At approximately 4:00 eastern time, Operation: Payback changed its target to www.visa.com. The site was taken down within three minutes, and is currently down.

UPDATE, 12/9, 10 AM EST: Operation: Payback, whose Twitter account was deactivated after yesterday's Visa attack, is back this morning with a new target - Amazon - and notice that the attack will begin in two hours.

(James Bickers contributed to this story.)