ALF (Animal Liberation Front) is a direct-action animal rights group and much like PETA has been heavily criticized as employing tactics similar to those employed by eco-terrorists such as ARM.
ALF is well-known for raiding labs, farms and other businesses in order to liberate animals back into the wild, although this is well-intentioned sometimes this causes more damage to the wild than ALF realizes: an infamous exampled occured when members of ALF liberated a farm of mink only for the mink to kill many native wildlife, including endangered birds.
ALF are also accused of threatening violence against labs and farms they see as mistreating animals, much like PETA, ALF does not see their actions as terroristic and believe they are fighting for animals that can not defend themselves.
ALF and PETA are not considered terrorist organizations (unlike ARM) and like many direct-action groups can be viewed as heroes by some and dangerous fanatics by others - with ALF and PETA the controversy mainly comes from their methods rather than their actual goals. They also caused major vandalism, and also robbed pets and other animals.