A virus is nothing but software that connects itself to some other software which a user actually intends to use. It has the ability to duplicate itself by joining itself to other programs. For instance, a virus can append itself to a word document. Every time this word document runs it enables the virus to run and create copies of it which in turn proceed to infect other files and areas of the system.
In technical terms, a virus is a tiny code of program which finds a host and gets attached to it. Then the virus multiplies by making its own copies and also harms the host system along the way. A program, network or an operating system all act as hosts for a computer virus. It eats away the resources of the host like the hard disk and virtual memory which results in the deletion of useful data unknowingly and at times even deliberately on part of the infecting virus. Since a virus is a nothing but a program it can be written by any programmer using his own source code.
Although some viruses are written for useful purposes, a majority of them are created to wreak havoc in the targeted network or system. Sometimes programmers lose control of a program and they end up acting like a virus. These are very rare cases. There are two main factors which determine whether a program is a virus -
1. It should be self executing. It places its own code in the course of execution of another program which when run inadvertently enables the virus to run as well.
2. It should be able to reproduce and generate copies of itself.
There are five types of basic viruses:
1.File infector viruses are those which generally affect the program files. The.com and.exe files are generally the ones infected by this kind of viruses. The virus replicates after it has been executed by the original file it had corrupted and then spreads to corrupt the other files in the system which may eventually cause damage to the entire file system. In the end it stays stuck to the system and any file that is run on the system automatically gets corrupted by the virus.
2.Boot sector virus generally affects the boot record on floppy disks as well as hard disks. It attaches itself to a boot record which runs and replicates when the system is booted. This kind of virus also stays in the memory permanently and affects all the files that are newly added to the system.
3.Master boot record virus acts in the same manner as a boot sector virus. The only difference being the area where the infection takes place.
4.Multipartite virus has the capability of infecting both boot records and system files alike making it a very dangerous type of virus to get rid of. If only one part is clean and the other remains infected then the infection spreads from one part to the other. For example, if only the boot sector is cleaned and the file system remains infected than the boot sector will gradually be infected again by the virus in the file system. Both the areas need to be cleaned to get rid of this virus.
5.Macro virus generally infects data files and is also the most commonly known virus type. It can corrupt data files and also other system files.
Fri, Dec 18, 2009
Computer