What is a computer virus?
In recent years, computers have taken over almost all spheres of our life. The computer revolution received a major jolt when computer viruses intruded into the computer and started infecting them. The basic purpose of a computer virus is to damage the program and spoil the operational mechanism. But do you know what a computer virus is?
A computer virus is a software program that spreads and infects other programs in the computer by either modifying or destroying them. It also spreads or propagates or has the potential to do so.
A computer virus has at least the following four characteristics:
1. The set of computer instructions;
2. It is deliberately created and released;
3. It propagates using host programs;
4. It does undesirable things like causing damage or spoiling the operational mechanism, with malicious intent.
From the above, it implies 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 broadly classify into two types:
1. Resident viruses 2. Non-resident viruses. Resident viruses are those, which on execution install their code in the memory of target computer and infect other programs or discs. On the other hand, non resident viruses do not install themselves in the 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; and 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 someone 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 move on to the next phase of infection.
In the next phase, a virus spreads and infects other programs or disks. The virus also spreads on to 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 on to the final stage of action, which results in damage that we all know about.
Several preventive measures exist to safeguard the programs from virus attacks. For example, the software should be obtained from genuine and authorized sources. Unauthorized people should not be allowed to handle or use the computer.
Normally, floppies belonging to other computer users should not be used and if used, they should be checked for any virus, with the help of anti-virus programs available for this purpose. Important data and program files should have adequate back-ups or extra copies. Periodic scans should be done with some good anti virus programs. Reference C.K.B by Dr.C.L.Garg.
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