Q:- Which was the first computer virus?-> Elk Cloner...
It was written around 1982 by a 15-year-old high school student named Rich Skrenta for Apple II systems.
It was a boot sector virus. Whenever a infected floppy disk was used for booting a computer a copy of the virus was placed in the computer memory. And when a disk was inserted elk cloner would get copied to the disk thus spreading from system to system. In every 50th boot it would display a short poem:-
Elk Cloner: The program with a personality
It will get on all your disks
It will infiltrate your chips
Yes, it's Cloner! It will stick to you like glue
It will modify RAM too Send in the Cloner!
However Elk cloner did not caused any deliberate damage.
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.
There are different types of computer viruses with different objectives but they can be 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 from there. Whereas 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: – In this phase the virus enter into system but does nothing destructive to arise the user suspicion. When one uses the infected at this stage he finds nothing abnormal and continues. This gives the virus a chance to go into the next phase of infection.
2) The propagation phase:- In propagation phase virus spreads as far as possible and infects other programs or disks. The virus also spreads into other systems via networking. This is the most damaging phase as the virus spreads from site to site, system to system and the user unknowingly helps in the propagation of virus.
3) Triggering phase: - The third phase or the triggering phase when the virus gets ready for the final act, that is, damaging.
4) The action phase: - Then comes the final stage of action which results in damage of the file.
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