A student from Northampton has been convicted of participating in a spate of denial-of-service attacks against companies including PayPal, Visa and MasterCard.

Christopher Weatherhead was convicted on a charge of "conspiring to impair the operation of computers" for participating in the attacks, organised in 2010 by the hactivist group Anonymous.

Anonymous targeted PayPal, Visa and Mastercard for blocking payments to transparency group WikiLeaks – reportedly on the request of US secretary of state Hilary Clinton. PayPal said the attacks cost it £3.5 million in lost trading and increased security spending.

It also attacked the websites of  record label and club Ministry of Sound, the British Recorded Music Industry (BPI) and the International Federation of the Phonographic Industry (IFPI).

Three other UK-based participants have already pleaded guilty to the charges. Weatherhead is now awaiting sentencing.