A computer virus is an illegal and potentially damaging computer program designed to infect other software by attaching itself to any software it contacts. 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 used to start the system. When the infected boot program executes, the virus is loaded into the computer's memory. Once a virus is in memory, it can spreads to any floppy disk inserted into the computer. A file virus inserts virus code into program files.
The virus then spreads to any program that accesses the infected file. A Trojan horse virus (names 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 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 memory or disk space remains. To detect computer viruses, antivirus programs have been developed. Besides detecting viruses, antivirus programs also have utilities to remove or repair infected programs and files. Some damaged files cannot be repaired and must be placed with uninfected backup files. The table below...