There is ALF and ELF, they are both left wing terrorist groups.
ELF stands for Earth Liberation Front. They are known for throwing caltrops/spike traps at logging trucks, they burn down houses in forested areas, they get together in armed mobs wanting to go beat up loggers. They basically tree forgeters.
ALF stands for Animal Liberation Front. They do similar stuff, but in the name of animals instead of trees. Basically a more militant PETA.