A computer virus is an illegal and potentially damaging computer program designed to infect other software by attaching itself to any software it comes in contact with. In many cases, virus programs are designed to damage computer systems maliciously by destroying or corrupting data. If the infected software is transferred to or accessed by another computer system, the virus spreads to the other system. Viruses have become a serious problem in recent years, and currently, thousands of known virus programs exist.
Three types of viruses are a boot sector virus, file virus, and Trojan horse virus. A boot sector virus infects the boot program. When the infected boot program executes, the virus is loaded into the computer's memory. Once the Virus is in memory, it can spread to any floppy disk inserted into the computer. A file virus inserts virus codes into a program file. The virus then spreads to any program that accesses the infected file.
A Trojan horse virus (named after the Greek myth) hides within or is designed to look like a legitimate program.
Some viruses interrupt processing by freezing a computer system temporarily and then displaying sounds or messages. Other viruses contain time bombs or logic bombs. A time bomb is a program that performs an activity on a particular date. A logic bomb is a program that performs an activity when a certain action occurs, such as an employee being terminated. A worm, which is similar to a virus, copies itself repeatedly until no more memory of disk space remains.
To find computer viruses, anti-virus programs have been developed. Besides detecting viruses, anti-virus programs also have utilities to remove or repair infected programs and files. Some damaged files cannot be repaired and must be replaced with uninfected archive files.
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