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Thursday, December 17, 2009

Types of computer viruses

There are many kinds of computer viruses. They come in a wide variety. The level of the destructiveness of viruses varies widely. Some viruses display pictures and massages on the screen. Others erase or destroy programs and data. The various types of viruses are:

1. Boot sector Virus
2. Program virus of file virus
3. Multipartite virus
4. Stealth virus
5. Macro virus

1. Boot Sector Virus

Boot sector virus is developed to destroy or infect the boot sector of the disk where, Master Boot Record (MBR) is stored. MBR is a small program, which is responsible for booting the computer system. The boot sector viruses modify MBR that prevents you from being able to boot or ‘start up’ the computer from the system disk. By using the infected disk or CD during the booting, such types of viruses transmit automatically in the computer system. Examples of such viruses are Danish Boot, Devil 941, Disk killer, etc.

2. Program or file virus

A program virus or file virus infects application programs. They may attach themselves to any exec tension. BIN, .COM, EXE, .DRV (driver) and SYS (device drive). These viruses take control after the initial use of the infected program. Once the infected program is executed, it remains present in the main memory (RAM) even if the closed. When you execute another new file the virus attaches itself from the main memory in the new file. In this way all file or they may also overwrite, so it disturbs the file from executing. Examples of such viruses are Acid Rain, Alien.298 and crazy. A.


3. Multipartite Virus
Multipartite Virus have combination features of boot sector viruses and program viruses; they can infect both the application programs and the boot sector of a disk. They infect program files, and when the infected program is executed, these viruses also infect the boot record. When you boot the computer next time, the viruses load in memory from boot record and then start infecting other program files on the disk. Examples of such viruses are invader, Flip, Tequila, etc.

4. Stealth virus

Stealth virus is one of the most dangerous types of viruses which rarely gives information about the presence of it in your computer system. Generally, it infects program file and boot records. It is really difficult to detect this virus because it attempts to hide from the operating system and antivirus software of the computer and it uses a unique technique to ignore the detection. Examples of such viruses are Frodo, Joshi, Whale, etc.

5. Macro Virus


A Macro Virus is a new type of computer virus that infects the software document or template created using word processing or spread sheet software. When you open a word processing or spreadsheet document, the macro virus is activated and it infects the normal template or a documents. Since this virus attaches itself to documents, the infection can spread if such documents are opened on other computers. Examples of such viruses are DMV, Nuclear and word concept.





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