A London jury convicted a 22-year-old student and member of the hacking group Anonymous on Thursday of taking part in cyberattacks on several major companies' computer systems.
Self-described "hacktivist" Christopher Weatherhead showed no emotion after being convicted of conspiracy to impair the operation of computers. The attacks hit the sites of MasterCard, Visa, PayPal and several others. Weatherhead, who will be sentenced at a later date, could face up to 10 years in prison.
Three co-conspirators of Weatherhead pleaded guilty to the same charge in January and March.
Prosecutor Russell Tyner said Weatherhead and the others targeted companies in the music industry involved in combating Internet piracy and firms that had stopped processing online donations to the data-leaking site WikiLeaks. Tyner said the attacks cost these companies more than 3.5 million pounds ($5.6 million).
Working under online nicknames including "Nerdo" and "NikonElite," the group hit their targets with denial-of-service attacks — a technique that works by overloading a website with traffic.
They also used Facebook and Twitter to recruit followers and publicize their attacks, according to police.
The cybercrime spree focused attention on Anonymous, a loose-knit collection of Web-savvy activists and Internet pranksters — many of whom have targeted governments, officials or corporations over a variety of political grievances.