A virus is a program which has been written to interfere with the normal functioning of the computer. It does this by clogging the memory of the system by making copies of itself or it may destroy critical information used by other computer programs.
There are three main types of viruses: Boot sector viruses which infect the boot sector in the hard disk and affect the partition table, File viruses attach with executable files. The commonly infected files are those with COM or EXE extensions. The third, System viruses infect specific system files such as command.com. Computer viruses can be grouped into Time Bomb, Trojan Horse, Worm etc. Time Bomb will start on a particular date, at a particular time. The computer will lose its ability to function properly.
The virus known as Trojan Horse will enter into a computer through an e-mail or free programs that have been downloaded from the internet and cause plenty of damage. Viruses known as Worms are constructed to infiltrate on the legitimate data processing programs and alter or destroy the data. Worm programs often use network connections to spread from one computer system to another system, thus, worms attach system that is linked through communication lines.
Protecting computer system using antivirus software
In case the virus is present, it becomes our duty to use some anti-virus software for preventing virus attacks in the future. Anti-virus software falls into two categories: Scanners and Integrity checkers.
A scanner is a program that will detect the virus by checking the files on the disk, the boot sector of the disk and programs in the memory by looking for the signature of the virus. The signature is a piece of program code that is unique to the virus. It is very necessary to update regularly the virus scanner that you have bought. This is essential because new viruses are constantly appearing.
Integrity checkers work using simple checksums or complicated algorithms or cryptographic checksums which check if a file has been modified. It may be boring for you to check for virus every time you run the system. But you should not worry. Help is at hand with HomeGuard a unique device which once fitted to the computer automatically scans in the background for viruses. If there are viruses found in the system, HomeGuard will clean it up automatically without even having to press a key.
Precautions to be taken against viruses
- Install a memory-resident program in RAM that will detect and warn if a virus is present.
- Do not allow hardware engineers or salespersons to put a write-enabled floppy into your computer unless they can guarantee that it is not infected.
- Backup copies of all programs and data files should be kept.
- Backup copies of programs should be held as read-only disks to prevent infection.
- At least 2 copies of the backup must be kept.
- Never boot your machine with a floppy from an unknown source.
- Always write-protect your disk when you use it in another machine.