COMPUTER VIRUS

A small program that gets into your computer and disturbs the normal functions of the computer and destroys the important data stored in the computer is called computer virus. The computer virus cannot damage hardware, only data or software is corrupted. The computer file (data or program) to which a virus is attached is called infected file.

A program, which is infected by a virus, is known as infected program. When an infected program is loaded for execution, the virus automatically loaded into memory and attaches to all those programs that are in memory or loaded into memory.
Causes of Viruses

Following are the means through which viruses may be transferred from one computer to another.

(i) E-Mail

Now-a-days, most of the viruses spread due to receiving e-mail messages that contains viruses. When a user opens such an infected message, the virus is also loaded into the computer memory and attaches copies of it-self with many other program files loaded into the memory. This virus is also transferred to other computers when e-mail messages are sent from the infected computer to them.

(ii) Networks

Another way of spreading virus is by using Internet and other networks. For example, when you download some executable file or data on the Internet or from a shared disk on the Network, the infected files may be attached with the downloaded data that ultimately infects the computer.

(iii) Removable Storage Media

One important means of exchanging data is through the use of removable media like floppy disks, CDs and flash devices. So, when you copy the data from one computer to another by using a removable media, the infected files can be transferred to your computer.

(iv) Pirated Software

The virus can also infect your computer by using pirated software. The software, which is installed into your computer without license is referred to as pirated software. Some companies may intentionally attach some virus programs into their software. This program will only activate when it does not find some special file like license file on your computer.