Kinds of different viruses

Macro viruses

These are known to be the most widespread viruses partly because of the popularity of programs for which macros are written. Moreover, being platform independent also adds to the overall threat posed by these viruses. In fact macro viruses are known to have already caused much more damage than almost any other type of known computer virus.

Network viruses

Again, these are also an extremely widespread type of virus. These viruses are found in Local Area Networks and are known to spread using the shared network resources. In fact they are so dangerous that if they enter a LAN, they can even choke the entire bandwidth of the LAN which means that doing any kind of work on the network becomes an extremely slow and painful task. Commonly known Network viruses include SQLSlammer and Nimda.

Logic Bombs

Yet another type of computer virus. They can be inserted in a computer program. The Logic bomb is triggered when any function of the host program or any other program is used. Common cases of Logic Bombs are known to have triggered on a given date, generally the April Fools Day or on Friday the 13th (A date considered to be unlucky in a number of countries all over the world). The logic bombs can even delete files if triggered.

Companion Viruses

Companion Viruses are known to be effective on MS-DOS based systems only and therefore all the 9X versions of Microsoft Windows are also affected by it. This is obviously a much smaller threat than it used to be. This virus is known to create new files with the .com extension, though there are some reports of it being capable of creating EXE files. As Windows XP, (the most common OS) is not based on DOS, the threat of these viruses is subsiding.

Boot Sector Viruses

Another really nasty type of virus is the Boot Sector Virus. These viruses are capable of damaging the hard drive itself because they reside in the Sector Zero and are capable of attacking the Master Boot Record of the drive. These viruses generally used floppy drives to spread and have started to decline as the usage of floppy drives has subsided.

Computer Virus?

A computer virus is an executable program. Depend on the nature of a virus, it may cause damage of your hard disk contents, and/or interfere normal operation of your computer.


What Viruses Don't Do!

Computer viruses can not infect write protected disks or infect written documents. Viruses do not infect compressed files, unless the file was infected prior to the compression. [Compressed files are programs or files with its common characters, etc. removed to take up less space on a disk.] Viruses do not infect computer hardware, such as monitors or computer chips; they only infect software.

How do Viruses Spread?

Viruses begin to work and spread when you start up the program or application of which the virus is present. For example, a word processing program that contains a virus will place the virus in memory every time the word processing program is run.

Once in memory, one of a number of things can happen. The virus may be programmed to attach to other applications, disks or folders. It may infect a network if given the opportunity.

Viruses behave in different ways. Some viruses stay active only when the application it is part of is running. Turn the computer off and the virus is inactive. Other viruses will operate every time you turn on your computer after infecting a system file or network.

How to Prevent a Virus Invasion!

1. Load only software from original disks or CD's. Pirated or copied software is always a risk for a virus.
2. Execute only programs of which you are familiar as to their origin. Programs sent by email should always be suspicious.
3. Computer uploads and "system configuration" changes should always be performed by the person who is responsible for the computer. Password protection should be employed.
4. Check all shareware and free programs downloaded from on-line services with a virus checking program.
5. Purchase a virus program that runs as you boot or work your computer. Up-date it frequently.