Virus is basically a small program. The difference between virus and any other program is that a virus manipulates and corrupts information of our computer. A computer virus is a software code that replicates itself. It spreads from program to program and disk to disk manipulating and damaging valuable data. The reasons which make it dangerous is its capabilities to make copies of itself that can be spread from one computer to another. Virus can activate on certain date or when we type a particular command or press a particular key.
The two main ways of spreading viruses are:-
1. Optical drives
In computer field there are five types of viruses found:-
1. File infector virus
2. Boot sector virus
3. Master boot record viruses
4. Multi partite virus
5. Macro viruses
Some popular viruses are given below:-
1. Scores virus
2. Brain virus
3. Rain Drop virus
4. Jerusalem virus
5. Trojan Horse virus and so on.
Virus can be cured with antivirus program. A good antivirus program is one that checks whether the system has been infected or not. These programs stop the viruses from affecting the system. This prevents the virus not to get a foot hold in the system. Some of the antivirus utilities refuse any program to make resident in RAM unless allowed by the user. The detectors warn users about the presence of virus after it has been loaded into the machine or disk. Some of the popular antiviruses are Norton antivirus, avira antivirus, MacAfee etc.