Close up of masked "Anonymous" protester, at the "Occupy Wall Street" protest on September 17, 2011.
Anonymous is a group initiating active civil disobedience and spread through the Internet while staying hidden, 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.