A Computer Virus is a program that can replicate itself whilst causing harm to your computer by replacing, corrupting or deleting important system files. The behaviour of the virus is commonly associated with the human-affecting pathogens of the same name.
A computer virus can replicate itself by infecting the Boot Sector of the computer. This way, the virus is activated and replicated each time the computer system is turned on.
It can also replicate itself by attaching itself to legitimate programs. Once those programs are activated, so is the virus.
The effects of a computer virus can be disastrous. A virus can modify, corrupt or delete files and cause the computer system to slow down. If the virus attacks important system files, it may cause sudden crashes, BSOD’s or even damage the system beyond repair!
It is possible for a virus to spread online or by an external device. Online, viruses can be sent from person to person by email, instant messaging or simply by clicking on a rogue website link!
However, viruses are not able to spread on their own; they have to be attached to another program or piece of data in order to infect another computer.
Some of the most successful viruses can also be classed as Computer Worms or Trojans due to their behaviour and distribution methods; previous examples of viruses, such as the “ILOVEYOU” virus and the “CIH” virus, caused financial billions in damage!