And one group, the Earth Liberation Front, stands among the nation's leading domestic terrorists in the eyes of the FBI.
"They're very specific. They're very detailed. They're very good at it," said James Jarboe, the FBI's Domestic Terrorism Section Chief.
It was ELF that claimed responsibility for May's simultaneous arson attacks on an Oregon tree farm and University of Washington labs in Seattle.
"My research is only aimed at helping the environment. Everyone's research here is only aimed at helping the environment," said University of Washington scientist Sarah Reichardt.
Genetic research was the alleged target in the $5 million university fire where Reichardt's work to save endangered plant species also went up in smoke.
"I wouldn't put an eco-terrorist label on it. I don't think anything they're doing is ecological or to save the earth. They're just plain terrorists. We don't call terrorists like Ted Kaczynski or Timothy McVeigh social terrorists. They are just terrorists," said Reichardt.
But who are they? Only four ELF members have ever been arrested teenagers connected to a New York arson attack last December. Other than a Web site that gives instructions on building fire bombs and a pamphlet that defends its violent methods, the face of ELF is said Oregon resident and ELF spokesman Craig Rosebraugh.
"What wasn't and still isn't told to the millions seeking the American dream, is that dream comes at a price," said Rosebraugh.
"The organization and myself consider the popular environmental movement to be largely a failure, a miserable failure in its efforts to protect the natural environment," said Rosebraugh.
He has been investigated but never arrested by federal and local authorities, who concede the profile of ELF members is murky.
"We have folks that have recently gotten into the movement. We have those who have been around for 20 or 30 years," explained Jarboe.
What also frustrates investigators from the Pacific Northwest to the East Coast is that they're not just dealing with one roving band of arsonists. Instead, they're confronted by an unknown number of ELF units occasionally working together, but largely operating on their own.
"ELF is a phantom. You are not going to be able to, I don't think, put ELF in a box and say this is what it is," said Thad Buchanan of the Eugene, Ore. police department.
With more than 140 arson fires in just the past 12 months, Eugene police say the challenge is just making a case.
"We think we're pretty close to solving a couple of those cases. But to say that they're part of this group, I can't say that," said Buchanan.
Meanwhile, the arson attacks have inreased some by ELF, some by copycats. And victims like researcher Sarah Reichardt have seen their lives change in ways they never expected.
"A month ago, if you'd asked me, I would have said I didn't want to live with security systems ruling my life because I didn't want a fortress mentality. And now I welcome them," admitted Reichardt.
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