Types of Computer Viruses
Types of Viruses on Computer
On the basis of their ways of infecting, viruses can be categorized into various types. Among them some common types of computer viruses are described below.
- Boot Sector or Start up Infector Virus: It is also called Boot record infectors virus. Start up infector virus infects the boot record or Master Boot Record (MBR) of the disk and replace the boot record program, copy elsewhere or overwrite it. This type of virus is loaded during the booting time and create the bad sectors on the disk and affect the entire computer system. This virus generally hides in the boot sector, in either the bootable disk or the hard drive.
- Boot Infector or Operating System Infector Virus: This is a common type of computer virus which infects the various parts of the Operating System or Master Control Program (MCP) and deletes and corrupts the system files necessary for booting. Thus, when these files are corrupted the Operating System cannot be loaded.
- Application Program Infector or File Infector Virus: These viruses infect the executable files or programs. An executable file can be a program file, like Word or Excel, Access, etc. They attach themselves to executable programs, such as word processors, spreadsheet applications and computer games which has usually .EXE or .COM extensions. These viruses directly attack and modify application program files. When an infected executable file is run, the viruses executes and does whatever it wants to do.
- Message Carrying Virus: This type of virus does not do any harm to the computer but it frequently displays the unwanted, vulgar message on the screen to irritate the user. It may be used to provide entertainment to the user in some extence.
- Polymorphic Virus: This type of virus encrypts its code in various ways and appears differently in each infection. Polymorphic viruses are harder to identify since each copy of the virus is different. Phoenix, Stimulate, Evil, Virus 101, proud and Cascade, etc are some examples of polymorphic viruses. They are also difficult to identify and remove by anti virus.
- Macros Virus: This type of virus infects the user related macros in application software with in a document or template. it is activated when we open the Word or Excel program and it affects the normal program and attaches itself.
- Multipartite Virus: These are the hybrid of Boot and program viruses. They infect the program files at the time of execution. Similarly, it is loaded at the booting time and starts infect the computer program.
- Worm: Worm is a self replicating or propagating virus that mainly damages the computer system. It is activated itself and makes multiple copies and fills the entire disk with copies of itself. It is basically spread through the network and Internet via email message attachments. Unlike a virus, it does not need to attach itself to an existing program.
- Stealth Virus: A stealth virus is a file virus, that uses special techniques to hide its presence from users and virus scanners.