If one is anxious to know what is a computer virus it is for certain that he might get a lot of answers which might appear to be complex. However the case is different in reality... There are certain basic issues involved in understanding the issue on what is a computer virus. A computer virus is a self-replicating computer program that behaves like a biological virus. It spreads by inserting copies into other executable code or documents. Similiarly like the biological virus it spreads on its own by multiplying itself throughout the system, just like the biological virus that spreads by inserting itself into living cells.

There are different types of viruses. Some of the prominent ones are Trojan horses , worms, and email viruses. The Trojan horses are computer programs which pretend to do one thing but actually do damage when they start it. The worms viruses are pieces of software that use computer networks and security flaws to create copies of itself. A cop y of the worm will then scan the network for any other machine that has a specific security flaw, and then replicate itself to the new machine. With regards to email viruses, these use email messages, and usually will copy and automatically mail itself to hundreds of people.

There are two generalities of viruses, including resident and nonresident viruses. Resident viruses are those viruses that contain a specific replication module which is alarmingly similar to t hose employed by nonresident viruses. A resident virus is one that stays in memory after it executes, and even after its host program is executed. Resident viruses are often subdivided into categories like fast infectors, and slow infectors. Fast infectors are those particular viruses which are designed to affect as many files as possible and slow infectors are designed to infect hosts infrequently. For instance some slow infectors will only infect files when they are copied.

Nonresident viruses on the other hand are those viru ses which consist of a finder module and a replication module. The finder module is responsible for finding new files to infect, while the replication module is the component that actually infects the found files. In the case of simpler viruses, what basically happens is that the replication module opens a new file, checks to see if the executable file has already been infected, appends the virus code to the executable file and saves the executable's starting point. It changes the executable's starting point so that it points to the start location of the newly copied virus code, saves the old start location so that the virus will move to that location immediately after its execution and then save the changes to the old executable file. Finally it closes the infected file and returns to the finder so that it can find even more files for the replication module

The History Of Computer Viruses

If you have been wondering on issues like what is computer virus, what are computer viruses, and where do computer viruses come from, the actual fact is that viruses have been around for longer than most people think. In fact, the first PC virus was created in 1986. This is popularly called 'Brain' virus, and was written in Pakistan. This particular virus was a boot-sector virus, as it could only infect the boot records and not hard drives. It would occupy the unused space on the disk so that it could not be used, and as well as be able to hide itself from detectio n. The reason is that it would display the original and uninfected boot sector when a user tried to view the infected space on the disk. With the fast progression of technology, computer fraud is becoming more complex and common. A Criminology degree online educates and informs you on how to stop this fraud and other scams.

It was in 1987 that the Lehigh virus was established, and it was first discovered at Lehigh University, hence the reason for its title. This was in fact the first memory resident file infector. They attack executable files. In March 1998 the first anti-virus was written, and it was originally designed to detect and remove the Brain virus. This was made possible by immunizing against the Brain infect ion as well.

The questions of what is a computer virus, what are computer viruses, when is a computer subject to infection by a virus, and why do people create computer viruses can not be answered simply, as there are many explanations and reasons for all of these. There are a number of different reasons as to why virus writers create these viruses. Some of them are research projects, pranks, vandalism, to attack the products of certain companies, to dis tribute political messages, for financial gain from identity theft, spyware, and cryptoviral extortion. However there are also some viruses that are intended to be good, as they help in improvement to the programs. It should also be known and remembered that a poorly-written good virus can still turn bad, as it may misidentify its target file and then result in deleting an innocent system file by mistake.