The most dangerous terrorist weapons in the world are not possessed by terrorist groups, but by the U.S. government Red Team organization. This is an outfit that specializes in thinking, and planning, like known, or potential, terrorist groups, and figuring out what kinds of attacks the terrorists might launch. What makes the Red Teams more dangerous is that the group has more resources than any terrorist group. This includes people who have access to everything the U.S. government has on Cyber War weapons, and details of vulnerable American infrastructure.
The problem is simple. American companies, including municipal utilities and air traffic control, are rapidly converting to web based remote control systems. In the past, remote access to factories, sewage or water purification systems, was via custom made, and expensive (to build and maintain) communications systems. It's so much cheaper to do it via the Internet. But Internet based systems are much more vulnerable that the older, custom made ones.
While business and government users know about this vulnerability, and install lots of defenses, the Internet is, well, just more vulnerable. And the Red Teams are always poking around to find out, as much as possible, about just how vulnerable. Now the Red Teams know that they are going to come with attack methods that few, if any, terrorist groups would have the resources to develop. Which is why the data compiled by the Red Teams would be so valuable, and destructive, if it ever fell into the hands of any terrorist groups.
The Red Teams secrets are stored on an air force base. Actually, the Red Teams are part of Sandia Labs, which is part of the Department of Energy (because the labs began as a nuclear weapons developer). All of these organizations have a lot of experience keeping secrets. That, however, can also be a shortcoming. The general public has little idea of exactly what the Red Teams do, how they do it and who they do it to. The government prefers to keep potential enemies in the dark by not commenting. However, there is a feeling that the Red Teams are concentrating too much on defenses, and not enough on going after potential Internet based terrorists. This can be deduced from the fact that any operations to take down Internet terrorists would show up in the news. Then again, there has been, as far as can be seen via open sources, no serious cases of Internet terrorism to date. So any offensive operations against potential threats would not, so to speak, show up on the radar (of general media coverage.)
The Red Team operation also serves commercial and foreign customers, performing security analysis of sites all over the world. This gives the counter-terrorism section of Red Team more information to work with. The Sandia Labs have a reputation for doing very good work, and having it done by very competent people. So, despite all the secrecy about who is doing, or capable of doing, what to whom with what, the good guys appear to have and edge over the terrorists.