(CN) - So-called "hacktivists" pleaded guilty in Federal Court to attacking PayPal after the payment service severed ties with whistleblowing website WikiLeaks.
Thirteen members of the collective "Anonymous" targeted services including Mastercard, Visa, and PayPal because they stopped processing payments for WikiLeaks, which has published troves of classified diplomatic cables and documents, the Justice Department said.
U.S. Attorney Melinda Haag said in a statement that the denial of service - known as DDoS - attacks codenamed "Operation Avenge Assange" were a coordinated effort intended to make the access to payment websites impossible.
"These DDoS attacks were facilitated by software tools designed to damage a computer network's ability to function by flooding it with useless commands and information, thus, denying service to legitimate users," the Justice Department said.
Anonymous, which first came to prominence in a long-running campaign against the Church of Scientology, allegedly made the software available for free download on the Web and carried out the attacks in December 2010.
PayPal froze WikiLeaks' account for violating of its terms of service. WikiLeaks responded to the ban by claiming PayPal "tried to economically strangle" it, according to the Justice Department.
The multiagency prosecution of the Anonymous defendants - 11 men and two women - included efforts from the FBI, with cooperation from PayPal and assistance from the National Cyber-Forensics and Training Alliance. Authorities in the Netherlands, Germany and France also investigated the attacks, the Justice Department said.
Ten of the hacktivists pleaded guilty to felony conspiracy misdemeanor intentional damage to a protected computer charges last week in San Jose, Calif. Three others pleaded guilty to the misdemeanor charges only.
All are currently free on bond. U.S. District Judge D. Lowell Jensen will sentence the hacktivists late next year.
One of the defendants, Joshua Covelli, also pleaded guilty to a separate cyber attack on Santa Cruz County's website. He claimed the attack was in retaliation for a statute that prohibits camping within Santa Cruz city limits, according to the Justice Department.
Covelli and others - calling themselves the "People's Liberation Front" or "PLF" and claiming to be associated with "Anonymous" - referred to the coordinated attacks as "Operation Peace Camp 2010."
WikiLeaks, founded by Australian activist and publisher Julian Assange, continues to publish diplomatic cables and other classified media on its website, which was launched in Iceland in 2006.
Assistant U.S. attorneys Matt Parrella and Hanley Chew prosecuted the case with the assistance of Elise Etter.
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.