Now unfortunately for perhaps the good people, the people in the white hats, the defensive programs have been far outstripped by the offensive programs. It is much easier to build a gun than it is to build a wall that is going to stop this kind of weapon. The offensive tools generally do very simple things. They can either, as Geoff commented, they can disable a machine by a denial of service attack of some other form of attack. They allow you to spy on people, capture transmissions, or they essentially allow you to take control of the machine, whether it is individual files, or the actual hardware itself.
Programs can do anything to a computer.
Anything that can be done by a human being typing on a computer can be done by a program that takes over the computer. I just want to emphasize that in 1988, probably one of the most influential and famous security programs ever was released, the Internet Morris Worm written by Robert T. Morris. What it did is, at the time the Internet was at about 50,000 systems, broken into about 10 percent of the systems, about 5,000 systems, and it was just as if someone was individually typing in and attacking all of these systems by hand. But the age of automation makes this considerably more easy and very much more effective. Almost 10 years later now, this last December, I decided to take a look at the network today and to examine whether we have gone any further.