Initiated by Anonymous and dubbed "Operation Payback", the campaign was aimed at movie and music industry organizations at the beginning, and then at PayPal, MasterCard, Visa and other financial institutions for refusing to process donations to WikiLeaks.
Russell Tyner, Crown Advocate for the CPS Organised Crime Division, said before the court that the attacks executed by Weatherhead and his fellow conspirators cost the targeted companies over £3.5 million in additional staffing, software and loss of sales.
"These were lawful companies with ordinary customers and hard working employees. This was not a victimless crime," he claimed.
Weatherhead's conspirators and Anonymous members Peter Gibson, 24, Ashley Rhodes, 28, and Jake Birchall, 18, pleaded guilty to the same charge earlier.
During the trial, Weatherhead insisted that he had not taken part in the attacks and that he was acting only as a "communications manager" and "online chatroom creator" for Anonymous," The Guardian reported.
In spite of these claims, he was found to be guilty by a jury and will be sentenced in January.
Until then, he has been released on bail and has been ordered not to use internet chat relays or post online under his known pseudonym or any other name but his own. He also has to wear an electric tag and will have to abide to a set curfew.