The FBI’s top domestic terrorism officer yesterday called the Earth Liberation Front and its companion, the Animal Liberation Front, the largest and most active U.S.-based terrorist organizations. According to the FBI, the two organizations have perpetrated a total of 600 attacks since 1996 costing $43 million in damage. The bureau acknowledged, however, that no one has ever been killed in the attacks, meaning the organizations are not as dangerous as others tracked by the FBI. Congressional efforts to investigate the groups have been frustrated by the refusal of former ELF spokesperson Craig Rosebraugh to testify. Meanwhile, Mark Warren Sands, the Phoenix man who committed eight acts of arson in the name of protecting the Earth, has been sentenced to 18 years in prison and $2.8 million in restitution.