Animal Liberation Front
The Animal Liberatin Front (ALF) is an international radical animal rights network, that engages in direct action and illegal activities to get closer to their goal of animal liberation. ALF was founded in 1976, from the ashes of the animal rights group Band of Mercy.
Structure & Activism
ALF is not an organisation in the strict sense, but rather a network of leaderless groups that all claim the name of ALF. Everyone who works to further the cause of animal rights while striving not to harm humans or non-humans in the process can proclaim themselves members of ALF. In this sense it's very similar to Anonymous.
Among other things ALF does, they are most famous for freeing animals from laboratories and factories.