The American University in Cairo
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A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate themselves. All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce.

Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networks and bypassing security systems. Since 1987, when a virus infected ARPANET, a large network used by the Defense Department and many universities, many antivirus programs have become available. These programs periodically check your computer system for the best-known types of viruses.


Some people distinguish between general viruses and worms. A worm is a special type of virus that can replicate itself and use memory, but cannot attach itself to other programs.

History of Computer Viruses | F-Secure Security Information Center (Latest Viruses and Virus Statistics | How Computer Viruses Work | McAfee | US-CERT Computer Virus Resources | Search for Viruses | Symantec Security Response

An Overview of Computer Viruses and Antivirus Software | Computer virus | The Skinny on Computer Viruses.