A Computer Virus is malicious coded program that is used to infect a computer and disrupt its normal operations by making changes.
A Computer Virus is malicious coded program that is used to infect a computer and disrupt its normal operations by making changes in the registry. Once a virus infects a computer, it will try to infect as many files as possible in a short span of time while trying to avoid detection. The term computer virus is a broad term which covers all sorts of malware like Spyware, worms, Trojans and actual viruses. But whatever might be the case, the purpose is to harm the computer. The intentions of a virus is to infect the victim computer and cause damages ranging from as small as slowing down a computer to as big as stealing sensitive data or causing physical damages to the hardware.
History of Virus:
In its initial days virus was not called by the name virus. It was known as "Self Reproducing Program" that is, a program able to reproduce itself where it resides. This concept was defined by John von Neumann in 1949. For the first time in the year 1984 Fred Cohen, in his research paper "Computer Viruses - Theory and Experiments" explicitly mentioned the term "Virus".
The first virus to be detected was in the networks of ARPANET and was called "Creeper Virus". The intention of the virus was not to cause any sort of damage, but was to understand the mobility and reproduction of the virus where it resides.This virus was released into a controlled area and was well taken care off. The first virus to be released outside a controlled area, that is, outside any lab, was called ""Elk Cloner". This virus targeted Apple OS computers. The virus was intended as a practical joke by its creator and caused no harm.
The first virus to cause harm was called "(c)Brain" and was created by Farooq Alvi Brothers from Lahore, Pakistan in the year 1986. The purpose of this virus was to protect the software written by its creators from piracy. It caused the floppy drive to slow down. In the earlier days before the common use of computer networks, viruses spread from one computer to another via floppy disks, as these were the only means of transferring data from one computer to another. Since then, computer virus have become more advanced and complex.
What does a virus do?
Let’s imagine a desk clerk coming to work every day to his office. Every day he finds a stack of papers with a list of tasks, which he must fulfills during his working day. He takes the top paper from the stack, reads the instructions of his superior and follows them carefully, and then throws the "used" papers into waste basket. Suppose a bad guy sneaks into the office and inserts a paper into the stack with his own task, which instructs the clerk that "Copy this paper two times and put the copies into neighbors' stacks”. What will the desk clerk do? He will copy this paper twice, destroy the original one and continue to the next paper in the stack, i.e., will go on working as usual thinking that he has committed no wrong. And what will his neighbors do?
They will do the same thing as the first one did: copy the paper twice and give it to other desk clerks. Altogether we have four copies of this particular paper already, and the paper will continue to be copied and transferred to other people. It is approximately in this scenario that the computer virus works, with programs instead of papers stack and computers instead of desk clerks. A computer like a desk clerk carefully fulfills all the commands contained in a program (task lists), starting from the first one. If the first task is "copy my body into two other programs", the computer will do so, and the virus command will now be in two other programs. When the computer starts running other "infected" programs, the virus will continue to spread all over the computer in a similar manner.
In the above example about a desk clerk and his office our paper virus does not check whether another stack of papers is infected or not. In this case by the end of the working day all the office will be overrun by piles of such copies, the clerks will have nothing else to do but copy the same text and give it to the neighbors. The first clerk makes 2 copies of the paper, the next victims of the virus make 4 copies, then 8, 16, 32, 64 and so on, and the number of copies each time will increase twice. If a desk clerk needs 30 seconds to copy one paper and 30 seconds more to pass the copies on, then in an hour there will be more than 1000,000,000,000,000,000 copies of the virus in the office. Soon, of course, the office will be out of paper, and spreading of the virus will be stopped because of this obvious reason. It happened in 1988 in America, when several global information networks became overflow with copies of a network virus "Morris's Worm", which transferred itself from one computer to another.
As now day’s users are more aware about the viruses, than in previous days, still viruses manage to infect computers even with the most advanced security system in place. This is so due to the fact that security systems follow viruses and then patch themselves. That is, when a new virus is released, then only security systems can recognize it and patch themselves. It is almost impossible for the security systems to predict any new virus before they are released. Strategies for infection are defined into two categories and they are as follows.
In this type of strategies, the virus has two modules. One is called Finder Module and the second is called Replication module. The Finder Module finds potential files to infect and once they are found, Finder Module calls upon the Replication Module to infect the file.
In this strategy there is only one module the Replication Module. In this scenario the virus loads its Replication module in to the memory of the operating system, so that when ever the operating system is executed the virus will also execute along with it.
Protection Against Virus:
The foremost thing in protecting one self from viruses is to be aware, that how viruses infiltrate and what are the carriers for the viruses or in other words what are the doorways for the virus to enter a computer. Once a user is aware of these facts, rest is a simply task of keeping the security systems updated. A user must at all times have and effective and efficient security system, in this case an Anti-Virus. An anti-virus is a program which will protect the computer from being infected from virus attacks. But to ensure complete protection from an anti-virus, one must regularly update his/her anti-virus program. Keeping an updated anti-virus is very important or else there is no point in having an outdated anti-virus program.
When an anti-virus is updated it downloads patch files from its servers to recognize new viruses. Lets consider the example of a police officer who can recognize all the criminals in a particular area because; the police officer has been shown their pictures at the headquarters. But if there is a new criminal in the area and the police officer is not shown his picture, the police officer will fail to recognize the criminal, even if he is standing in front of the officer. Same is the case with anti-virus. An updated anti-virus is able to detect any sort of a new virus, thus reducing the chances of having one’s computer infected.
Who Creates Viruses And Why?
Mainly students having just studied the "Assembly Language" they would like to try something but cannot find anything more decent to do. One can only be glad that mostly such authors do not spread their viruses themselves, and after sometime these viruses "die" together with the diskettes they are kept on. Those kinds of viruses are created only to raise one's self respect.
The second group consists also of young people (often students), who are not experts in programming yet, but have already decided to devote themselves to creating and spreading viruses. The only reason moving such people to create viruses is their inferiority complex, resulting in computer misdemeanors.
The third group is the most dangerous. It creates and launches so called "Professional" viruses. These are very thoroughly thought out and debugged programs created by professional programmers, and often -by talented ones. Such viruses often implement original algorithms, undocumented system calls and unknown methods of incorporating into system data areas. Professional viruses in many cases utilize stealth technology and / or are polymorphic; they infect not just files but also boot sectors of drives and sometimes windows executable.
No matter what the reasons, virus program cause damage and harm. They are a social evil that exist on the internet.