Anonymous - The name of the eponymous, leaderless hacking group originated on 4chan in 2003, and it's believed that various members of Anonymous met there. In 2008, an unofficial spokesperson Trent Peacock described the group on a Canadian Broadcasting Corporation radio show:

We [Anonymous] just happen to be a group of people on the internet who need--just kind of an outlet to do as we wish, that we wouldn't be able to do in regular society. ...That's more or less the point of it. Do as you wish. ... There's a common phrase: 'we are doing it for the lulz.'

An oft-cited mission statement of sorts reads:

Knowledge is free. We are Anonymous. We are Legion. We do not forgive. We do not forget. Expect us.

Anonymous uses the Guy Fawkes mask from V Is for Vendetta as one logo and a headless businessman for others. Beyond iconography, however, the history of Anonymous is best told through a timeline of its projects.

Project Chanology - Though the name refers to its beginnings on 4chan, Project Chanology is widely recognized as Anonymous's first major coordinated effort and targeted the Church of Scientology. Anonymous declared war on the Church of Scientology after they attempted to remove a potentially condemning video of Scientologist Tom Cruise from the internet in 2008. Though that war took many forms--prank calls, black faxes, denial-of-service attacks--it all started with this YouTube video:

The statement in the video shows off the activist beginnings Anonymous: "For the good of your followers, for the good of mankind--for the laughs--we shall expel you from the Internet and systematically dismantle the Church of Scientology in its present form."

YouTube Porn Day - After the long fought battle with the Church of Scientology and a few other smaller projects, members of Anonymous teamed up with eBaum's World users to declare YouTube Porn Day on May 20, 2009. The protest itself, as the name sort of suggests, involved countless people uploading porn to YouTube to annoy the moderators who would then have to remove the videos. It took YouTube days to remove all of the videos. The group repeated the action in 2010 "in protest of YouTube's decision to suspend the account of Lukeywes1234," an otherwise typical user whose account was suspended for abuse language:

Operation Payback - Anonymous did some work around the 2009 Iran election protests and Australian internet policy, but they gained global notoriety as activists--or more appropriately, "hacktivists"--for their support for WikiLeaks. Although the project started in September 2010 as a war against the recording industry for opposing internet piracy, it evolved. Beginning in late November 2010, when the first U.S. diplomatic cables were released by WikiLeaks, Anonymous latched onto the cause and launched Project Avenge Assange, an attack on banks and credit card companies who froze WikiLeaks donations.