Computer viruses are mysterious and grab our attention because everytime a new virus hits, it makes a news if it spreads quickly. On one hand they show us how vulnerable we are, and on the other hand they show us how sophisticated and interconnected human beings have become.
It all started way back in 1950, when John Neumann authored a paper entitled "Theory and Practice of complicated automata". People at that time found the idea to be absurd and rejected it. All but a few, a few programmers kept the idea and as a result "Core Wars was born as a recreational game at AT&T Bell Labs in 1960's. Programmers would write a set of programs and set it free in memory to scan the programs written by other programmers and destroy the set if found. The set whose replica was most in the memory was the winner. This game was backed by senior programmers at AT&T. Boxes in those days were not connected in those days, so in case game goes wild, box was switched off. But the implication of such softwares was realized and it was decided never to reveal their existence to outside world.
Ken Thompson, of UNIX fame, was the first one to infringe this unwritten law of secrecy. In a public function, while delivering his speech, he revealed the existence of such games and also encouraged other people to ponder over the idea. Within a short time the world saw an new upcoming generation of computer programs, which incorporated the ability to replicate and destroy other softwares. Soon they came to be known as Viruses.
What is a computer Virus
As per Webopedia it is defined as " A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate themselves. All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce." I would love to define it as " A malicious code inserted into genuine software without users knowledge and permissions. It is an executable object having the capabilities to hide and replicate themselves into other executables and optionally having the capability of destruction."
The one outstanding feature that makes a virus is the capability to replicate itself. The virus sets out with the aim to replicate. People usually associates viruses with destruction but this is not essential for a program to be classified as computer virus.
Why it is known as a Virus
Computer viruses share some common traits of their biological counterparts. It replicates, passes from one system to others, may have capabilities to make your system "sick".
A Virus usually consists of following three sections
1.Replicator: This part ensures survival of virus. It is achieved by infection the legitimate executables or Boot parts.
2.Concealer: This ensures safety of viruses.
3.Payload: This can be practically anything from formatting your hard disk to emailing itself.
Other Rouge Softwares:
1.Trojans: These bear the name of a genuine software and allow the attacker to posses you
2.Chameleons: These bear the name of some legitimate program and usually mimic that program. A fake login program can mimic a correct login program to capture the passwords.
3.Bombs: These Get activated on some particular time and their payload becomes active at that time. It is said to be exploded at that time.
Ordinary Software Bombs: These explode as soon as activated.
Timed Software Bombs: These explode on some specific date and time.
Logical Software Bombs: These explode when some logical condition is met.
4.Worms: These have their own independent existence and replicate from machine to machine. Viruses are parasitic in nature whereas worms are not. Worms consume network resources.
5.Rabbits: These are like worms, standalone executables and work on standalone machine. When executed these replicate on disk until the capacity is full.
to be continued......