By day, Shannen Rossmiller is a mother of three and a part-time judge in a small town in Montana.
As night falls, she develops another persona -- she poses as an al Qaeda operative online and searches for would-be terrorists.
"It's important because the war on terror affects everybody, every single person, every day," Rossmiller said. "I have the skills to do it, so I feel it's something I have to do."
Rossmiller, 36, began trolling the Internet for potential terrorists after the Sept. 11, 2001, attacks. Stunned and angered, she read the Koran, studied radical Islamic culture, and learned enough Arabic to lurk in chat rooms.
"It was a process that evolved for me where the curiosity of looking around on the Internet for jihadi, Islamist extremist individuals," she said. "It's evolved now into something that is my own playbook on how to do this, and it worked."
Rossmiller's work first gained national attention when her online sleuthing helped federal agents set up stings that snagged two American extremists.
The first one was Washington state National Guardsman Ryan G. Anderson, a Muslim convert who wanted to give al Qaeda information about how to destroy U.S. Army tanks and Humvees, according to court records.
"I have no belief in what the American Army asks me to do," Ryan G. Anderson said on an undercover sting video. "They sent me to die to be away from my family for something I don't believe in."
With Rossmiller's help, Anderson was convicted of treason and sentenced to life in prison.
Rossmiller also manipulated Wilkes-Barre, Pa., resident Michael Curtis Reynolds into thinking she was a radical Islamist eager to underwrite his plan to blow up American oil and gag pipelines. She persuaded Reynolds to travel to an Idaho highway to pick up a bag containing $40,000. Instead, Reynolds was met by federal authorities alerted by Rossmiller.
In one e-mail that Rossmiller shared exclusively with "Good Morning America," she writes, "Your skills in nuclear physics are valuable to my group. … If the leaders approve of your membership, our sheik will be able to help with finances for your work."
The alleged extremist responds, "Where will we exercise the work? How will we meet to exercise the work?"
Rossmiller, who is not paid for her work, has expanded her search beyond U.S. borders. Her "hobby" comes with risks, but she says they are necessary.
"I take calculated risks, but they're thought out and they're careful. They're not irresponsible by any means," she said. "Because I can do what I do, it must be done."
Rossmiller says foreign intelligence officers have so far detained more than a dozen potential jihadists she has helped identify. Her work, however, is far from over.
"I'll be doing this for quite some time," she said.