What is computer virus?

Computer virus is a program that may disturb the normal working of computer without the knowledge or permission of the user. Virus attaches itself to the files in flash drives, hard disks and email attachments. A file containing a virus is called infected file. The virus is activated when the infected file is executed.

 

Types of viruses

There are 5 main types of viruses these are

 

1.both sector virus:

                                 A disk is divided into tracks and sectors. The disk that contains operating system has a special program in its first sector. The sector is known as boot sector. The program in boot sector is automatically loaded in memory when computer starts. The program then loads operating system in the memory.

                                           The boot sector virus modifies the program in the boot sector. It is loaded into memory whenever computer is turned on. The virus is attached with the executable files like .exa, .com and .dll files. When the user uses these files, the virus attached with these files is activated. It infects other files and performs destructive commands and destroys data files.

2.Chernobal Virus:

                                         The famous Chernobal virus deletes all Microsoft office files. It also deletes the partition information from the disk that causes a major loss of data. It also corrupts the system’s BIOS.

3.Logic Bomb:

                         Logic bomb is a virus activates when certain conditions are met such as opening a files or when certain data and time occurs etc. it is also called time bomb. Michelangelo is an example of logic bomb. It destroys data on the hard disk on march 06.

4.Trojan Horse:

                                   Trojan horse hides itself as useful program. It contains hidden instructions to erase data or cause other damage. It executes illegal, destructive instructions in the middle of a program such as computer game. FormatC is an example of a Trojan horse.

5.Redlof:

                    Rudolf is a polymorphic virus. It is written in Visual Basic Script. It relies on the Microsoft ActiveX component to excuse itself. It locates folders.htt and infects that file. Folder.htt is a part of Microsoft windows active desktop feature.