The first way terrorists can use computers is as a physical means of doing something. This could be something as small as spreading propaganda about the group. Terrorists can also obtain information through hacking into certain computers, they can communicate with each other more quickly and covertly with encryption, or they can use email for various purposes such as viruses and worms. One terrorist group that used email to accomplish a goal was the Tamil Tigers. The Tamil Tigers used email in order to fundraise their operations by hacking into Sheffield University and sending out a mass email to alumni encouraging a donation to a charity in Sri Lanka that they held the account for. ("Seminar On Cyberterrorism", Apr 16, 1998) These are just a few of the ways that a computer can be used to help accomplish a goal by terrorists.
Another way computers are used by cyber-terrorists is as a means of storing information that the group needs. Terrorist groups are able to store their finances, targeting lists, attack plans, and various other useful pieces of information on a single computer. By doing this, the terrorist groups are more organized making them more deadly. One example of this method involves Ramsey Youssef. After the first World Trade Center bombing, Ramsey Youssef's computer was seized upon becoming a suspect in the case. On this computer, plans were found outlining the bombing of 11 different planes over the Pacific. Although this was a victory in helping save those 11 planes, they may have never been found if Youssef's encryption code had not been found lying next to the computer. ("Seminar On Cyberterrorism", Apr 16, 1998) This aspect of cyber-terrorism is more commonplace in today's world with the ever-growing exposure of people to computers.
The third and quite possibly most dangerous way in which computers can be used in a terrorist attack is as the actual target of an attack.