Wikileaks Defenders Target Websites of MasterCard and Others

MasterCard Inc. and a Swiss bank that attempted to cut ties with Wikileaks are apparently feeling the wrath of Operation Payback — a group of hackers that are claiming to have shut down each company's website.

The websites appear to have been hit by a denial-of-service attack, which blocks public access by overwhelming a site with more traffic than it is designed to handle.

In an e-mail, MasterCard said it was experiencing "heavy traffic" at mastercard.com. "We are working on this to restore normal speed of service," the Purchase, N.Y., company said. Its website did not appear to be accessible on Wednesday morning.

MasterCard said Tuesday that it was in the process of suspending payments to Wikileaks. It is among several companies that have been attempting to cut ties to Wikileaks and its founder Julian Assange after Wikileaks exposed thousands of classified documents.

The website of one of the largest retail banking companies in Switzerland, PostFinance, which closed an account Assange held, has been inaccessible since Dec. 8, according to media reports.

"We are glad to tell you that http://www.mastercard.com/ is down and it's confirmed!" said Operation Payback on its Twitter account. "There are some things Wikileaks can't do. For everything else, there's Operation Payback." (The group also put out a YouTube video giving its raison d'être.)

Visa Europe and eBay Inc.'s PayPal have also said they are suspending the accounts for Wikileaks. Their websites remained accessible Wednesday morning.

Assange was arrested after turning himself in to British police Tuesday, media reports said, for a Swedish arrest warrant for alleged sex crimes.

The website of the Swedish prosecutor's office was also shut down, according to a statement from the agency, which said it was "impossible to get into our site due to overload" from Tuesday night until Wednesday morning.