Types of Computer Virus
Viruses may be classified under four major categories according to their nature and the way they infect a computer system.
1. Message Carrying Viruses:
These viruses do not infect the computer programs and do not damage data and information but display (pops up) interesting messages, pictures, dialogues, etc. which may entertain the computer user.
2. Boot Sector Viruses:
These viruses infect diskettes and hard disks and become active when an infected disk is used to start the computer. These viruses infect Boot Record, Master Boot, FAT and Partition Table,
3. System Infectors:
System infectors infect/destroy/corrupt the system files concerned with OS such as IO.SYS, MSDOS.SYS, COMMAND>COM, etc. These enter to the system as a device driver and get loaded into memory,
4. Application Infectors or Program Viruses:
These viruses infect computer programs (executable program files such as .COM, .EXE, OVL, .DRV, SYS, .BIN, etc.) and become active when the infected program is run,
Nowadays, some new category of viruses is also found which can be classified as:
a) Multipartite Viruses: These viruses show multiple features which can infect both programs and boot sectors.
b) Document Viruses or Macro Viruses: These viruses infect MS Word documents (files) through the macro programming capabilities of some newer programs. Macro virus becomes active when an infected document is opened, and the program opening the document has its macro capabilities turned on (enabled).
These viruses do not infect the computer programs and do not damage data and information but display (pops up) interesting messages, pictures, dialogues, etc. which may entertain the computer user.
2. Boot Sector Viruses:
These viruses infect diskettes and hard disks and become active when an infected disk is used to start the computer. These viruses infect Boot Record, Master Boot, FAT and Partition Table,
3. System Infectors:
System infectors infect/destroy/corrupt the system files concerned with OS such as IO.SYS, MSDOS.SYS, COMMAND>COM, etc. These enter to the system as a device driver and get loaded into memory,
4. Application Infectors or Program Viruses:
These viruses infect computer programs (executable program files such as .COM, .EXE, OVL, .DRV, SYS, .BIN, etc.) and become active when the infected program is run,
Nowadays, some new category of viruses is also found which can be classified as:
a) Multipartite Viruses: These viruses show multiple features which can infect both programs and boot sectors.
b) Document Viruses or Macro Viruses: These viruses infect MS Word documents (files) through the macro programming capabilities of some newer programs. Macro virus becomes active when an infected document is opened, and the program opening the document has its macro capabilities turned on (enabled).
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