Operation Payback is really a coordinated team of attacks on opponents of internet piracy by internet activists. It had been developed by users of 4chan, an online community which also gave rise to the Project Chanology attacks by Anonymous against the Church of Scientology as well as other internet memes.
Operation Payback started as retaliation to DDoS attacks on torrent sites, piracy proponents then decided to launch DDoS attacks on piracy opponents. The initial reaction snowballed into a wave of attacks on major pro-copyright and anti-piracy organizations, law firms, and individuals. In December 2010, following the United States diplomatic cables leak, the organizers commenced DDoS attacks on websites of banks who had withdrawn banking facilities from WikiLeaks.