What is a Computer Virus?

          Over the last few years computers have invaded almost all spheres of our life by increasingly playing a bigger and bigger role in various ways. The computer revolution got a major shock when computer viruses intruded into the computer and started spoiling the system. The basic purpose of a computer virus was to damage the programs in the computer and spoil the operational mechanism. But do you know what a computer virus is?

          A computer virus is a program that in one way or other infects other programs by either modifying or destroying them and it also spreads or propagates or has the potential to do so. A computer virus has at least the following four characteristics: 

1) It is a set of computer instructions, 2) It is deliberately created, 3) It propagates using host programs 4) It does undesirable things like causing damage or spoiling the operational mechanism. 

          From the above information it is implied that computer viruses are deliberately created software programs and should not be misunderstood as programming errors or hardware malfunctions. The virus engages itself in doing unwanted things like deleting files, formatting disk, changing the keyboard input etc.

          There are different types of computer viruses with different objectives but they can be broadly classified into two types:

1) Resident viruses, 2) Non-resident viruses

          Resident viruses are those which on execution install their code in memory and infect other programs or discs from there. On the other hand non-resident viruses do not install themselves in memory but spread when an infected program is run.

          There are four distinct phases of infection by a computer virus. They are: 1) The dormant phase, 2) The propagation phase, 3) The triggering phase, 4) The action phase. 

          In the dormant phase, the virus enters into the system but does nothing destructive to arouse the user’s suspicion. When one uses the infected program at this stage, he finds nothing abnormal and carries on without any suspicion which gives the virus a chance to easily go onto the next phase of infection.

          In the next phase, that is, propagation, a virus spreads out as far as possible and infects other programs or disks. The virus also spreads onto other systems via diskettes, communication links etc. This is the most damaging phase as the virus spreads from site to site, system to system without any apparent effort on their part; rather it is the user who unknowingly helps in the propagation of the virus.

          The third stage is the triggering stage when the virus gets ready for the final act that is damaging. Once the trigger is ‘pulled’, the virus moves onto the final stage of action. Then comes the final stage of action which results in damage that we all know about.

          Several preventive measures are there to safeguard the programs from virus attacks. For example, the software should be got from genuine and authorized sources. Unauthorized people should not be allowed to handle or use it. Normally, floppies belonging to others should be avoided and if used, they should be checked beforehand for any virus infection with the help of some special programs available for this purpose. Important data and program files should have adequate backups or extra copies. Periodic checkups should be done.

          Inspite of the measures if there is still a virus attack then either an expert should be consulted or the available virus cleaning programs can be used by experienced operators.