Traditional methods of using undercover sources and intercepting communications are largely ineffective against lone-wolf terrorists.
The Unabomber is locked away at the federal Supermax prison in Florence, Colo., but the memory of his attacks was dredged up after a string of packages exploded at homes in Austin this week.
Discovery Channel's "Manhunt: Unabomber" carefully unfolds the story of Ted Kaczynski, the infamous domestic terrorist whose bombing campaign lasted for than 20 years.
The Unabomber: Between 1978 and 1995, Theodore Kaczynski's ingeniously designed homemade bombs killed three people and injured 23 others.
In handwritten letters to hundreds of supporters and curiosity seekers, Unabomber Ted Kaczynski expressed shock over the 9/11 attacks among other things.