Anonymous (used as a mass noun) is an Internet meme originating 2003 on the imageboard 4chan, representing the concept of many online community users simultaneously existing as an anarchic, digitized global brain. It is also generally considered to be a blanket term for members of certain Internet subcultures, a way to refer to the actions of people in an environment where their actual identities are not known.

In its early form, the concept has been adopted by a decentralized on-line community acting anonymously in a coordinated manner, usually toward a loosely self-agreed goal, and primarily focused on entertainment. Beginning with 2008, the Anonymous collective has become increasingly associated with collaborative, international hacktivism, undertaking protests and other actions, often with the goal of promoting internet freedom and freedom of speech. Actions credited to "Anonymous" are undertaken by unidentified individuals who apply the Anonymous label to themselves as attribution.

Although not necessarily tied to a single on-line entity, many websites are strongly associated with Anonymous. This includes notable imageboards such as 4chan, Futaba, their associated wikis, Encyclopaedia Dramatica, and a number of forums. After a series of controversial, widely-publicized protests and distributed denial of service (DDoS) attacks by Anonymous in 2008, incidents linked to its cadre members have increased. In consideration of its capabilities, Anonymous has been posited by CNN to be one of the three major successors to WikiLeaks.

Source: wikipedia