The Federal Bureau of Investigation has raided a Dallas server farm that housed computers used to launch Internet attacks against PayPal Inc., according to an affidavit posted by TheSmokingGun.com.

The news website reported Dec. 29 that the search stems from a criminal investigation into the denial-of-service attacks that were launched against PayPal, Visa Inc., MasterCard Inc. and several other companies on Dec. 8 after those companies stopped providing their services to WikiLeaks. A denial-of-service attack works by knocking a website offline by overwhelming it with more traffic than it was designed to handle.

The FBI tracked the Internet Protocol addresses of the servers used in the online attacks to the Texas facility, Tailor Made Servers, the government document said. Server farms such as Tailor Made provide dedicated computers to companies, or people, looking to rent hard drive space. A message left for representatives of the server farm was not immediately returned.

As part of the December attacks, MasterCard said its SecureCode payment verification system was temporarily disrupted. Those attacks also took out MasterCard's main website and that of Visa. PayPal, a unit of eBay Inc., largely withstood the attack.

The FBI said those attacks were launched by an "internet activist group using the names '4chan' and 'Anonymous'." The group also launched attacks on Moneybookers.com, Sarah Palin's website, and the Swedish Prosecutor's Office.

On Dec. 12, Dutch prosecutors said they arrested a 16-year-old boy suspected of being involved in the cyber attacks.