Viruses: A virus is basically an executable file which is designed such that first of all it should be able to infect documents, then it has to have the ability to survive by replicating itself and then it should also be able to avoid detection.Computer viruses can be classified into several different types. Antiviruses: The ideal solution to the threat of viruses is prevention.

Do not allow a virus is get into the system in first place. This goal is in general difficult to achieve, although prevention can reduce the no: of successful viral attacksIn the mid-eighties, so legend has it, the Amjad brothers of Pakistan ran a computer store. Frustrated by computer piracy, they wrote the first computer virus, a boot sector virus called Brain. From those simple beginnings, an entire counter-culture industry of virus creation and distribution emerged, leaving us today with several tens of thousands of viruses. In just over a decade, most of us have been familiar with the term computer virus.

Virus: What exactly is a Virus?

A virus is basically an executable file which is designed such that first of all it should be able to infect documents, then it has to have the ability to survive by replicating itself and then it should also be able to avoid detection. Usually to avoid detection, a Virus disguises itself as a legitimate program which the user would not normally suspect to be a Virus. Viruses are designed to corrupt or delete data on the hard disk i.e. on the FAT (File Allocation Table).

TYPES OF VIRUSES

Computer viruses can be classified into several different types.

1. File or program viruses:

Some programs are viruses in disguise, when executed they load the virus in the memory along with the program and perform the predefined steps and infect the system. They infect program files like files with extensions like .EXE, .COM , .BIN , .DRV and .SYS. Some file viruses just replicate while others destroy the program being used at that time.

2. Boot Sector Viruses (MBR or Master Boot Record)

Boot sector viruses can be created without much difficulty and infect either the Master boot record of the hard disk or the floppy drive.

3. Multipartite Viruses

Multipartite viruses are the hybrid variety; they can be best described as a cross between both Boot Viruses and File viruses. They not only infect files but also infect the boot sector.

4. Stealth Viruses

They viruses are stealth in nature and use various methods to hide themselves and to avoid detection.

5. Polymorphic Viruses

They are the most difficult viruses to detect. They have the ability to mutate this means that they change the viral code known as the signature each time it spreads or infects.

6. Macro viruses

In essence, a macro is an executable program embedded in a word processing document or other type of file. Typically users employ macros to automate repetitive tasks and there by save key strokes