In one experiment, it caused the accidental denial of services due to a bit error.5.
Now that scientists knew what kind of damage could be done, they decided to avoid telling the public for as long as possible. It remained a secret until 1983, when Ken Thompson, author of UNIX, gave a speech about self-replicating programs. Two Italian readers, Cerutti and Morocutti, of "Scientific American" magazine described a program capable of passing from one computer to another via floppy disks.6 They ended up calling the program a virus and had thoughts about spreading it throughout their city.
The first example of a true virus was demonstrated at a seminar on computer security in November 1983, when Fred Cohen introduced a program that gained all system rights within thirty minutes.7 In January of 1986, two brothers running a computer shop in Pakistan designed a computer virus. They inserted the virus into software. By the end of 1988 at least 20,000 computers had been infected worldwide. .
Since the early 1980s computer viruses have become a lot more destructive. One survey found that ninety-eight percent of North American businesses have been infected by over 6000 types of viruses.8.
Virus Types and How They Work.
Computer viruses have become an epidemic. A National Computer Security Association report reveals that the rate of computer virus infection in corporate America tripled in 1996.9 Viruses should never go untreated.
Viruses come in many different shapes and sizes. The first kind is called a File Infector, which attach themselves to regular programs, such as COM or EXE files under DOS. They are invoked everytime a program is run. Cluster Infectors modify the file system so that they are run prior to other programs. Cluster Infectors do not actually attach themselves to programs. Macro Viruses are word processing documents that serve as sources of transmission for viruses that take advantage of the auto-execution macro capabilities in products such as Microsoft Word.