What is a Computer Virus?

Computer viruses are written (or programmed) by irresponsible programmers and hackers who believe that by writing such malicious and destructive programs, they are proving their ingenuity to the programming community and the world at large.

A computer virus is an undesirable and unwanted program file or routine that can corrupt files, replicate itself, replicate other files, or in some other way degrade or even shut down a computer system. It operates by finding and attaching itself to a system item, such as an executable program file, the boot record (computer startup area) or commonly used data-file-format files.

Most viruses stay active in memory until the computer is turned off. However, the virus is only removed from volatile memory (also known as random access memory or RAM), but not from the file, files, or disk it has infected. So, the next time the computer is switched on, the virus program is activated again and attaches itself to more programs.

Viruses are categorized by their infection targets. There are three types of viruses: program viruses, boot sector viruses and macro viruses.

Program viruses infect program files, which commonly have extensions such as .COM, .EXE, .SYS, .DLL, .OVL, or .SCR. The most common programs targeted by viruses are standard MS DOS applications that use the .COM and .EXE file extensions. Program files are attractive targets for virus writers because they are widely used and have relatively simple formats to which viruses can attach.

Boot sector viruses infect the system (non-file) areas of hard and floppy disks. These areas offer an efficient way for a virus to spread from one computer to another. Boot viruses have achieved a higher degree of success than program viruses in infecting their targets and spreading.

The latest threats to the computing public are macro viruses which infect data files with macro capabilities. For example, Microsoft Word document and template files are susceptible to macro virus attacks. They spread rapidly as infected documents are shared on networks or downloaded from Internet sites.

There are a number of virus detection packages available to prevent computer systems from being infected by virus programs. Popular and trustworthy packages include McAfee's Anti Virus, PC-Cillin and Norton AntiVirus.

New viruses spring up from time to time and, therefore, anti virus programs have to be updated as often as possible. Symantec Corporation (which produces the Norton Utilities and Norton AntiVirus programs) is an excellent service provider. The complete Norton System Works package, which includes Norton AntiVirus, comes with the LiveUpdate utility. Users can configure this utility to automatically check for the

latest virus definitions available at Symantec AntiVirus Research Center's (SARC) website via the Internet and to automatically download and install the latest definitions in their computers.