The fear has been there since 911: terrorists will somehow get their hands on nuclear weapons. That could mean an actual big weapon, a suitcase nuke (rumors have swirled around in some quarters for several years that they may already have one), or some kind of “dirty bomb” that may not be as sophisticated as one of the bigger ones, but have a huge impact nonetheless.
And then there are the reports that a marketplace for nukes could be Russia or countries in that area in the world. Rumors? A reporter posed as a terrorist and look what he found out.