What is a Virus ?

Robert Thomas, an engineer at BBN Technologies developed the first known computer virus in the year 1971.

The first virus was christened as the “Creeper” virus, and the experimental program carried out by Thomas infected mainframes on ARPANET.

The teletype message displayed on the screens read, “I’m the creeper: Catch me if you can.”

the original wild computer virus, probably the first one to be tracked down in the history of computer viruses was “Elk Cloner.” The Elk Cloner infected Apple II operating systems through floppy disks.

The message displayed on infected Apple Computers was a humorous one.

The virus was developed by Richard Skrenta, a teenager in the year 1982.

Even though the computer viruses were designed as a prank, it also enlightened how a malicious program could be installed in a computer’s memory and stop users from removing the program.

It was Fred Cohen, who coined the term “computer virus” and it was after a year in 1983. The term came into being when he attempted to write an academic paper titled “Computer Viruses – Theory and Experiments” detailing about the malicious programs in his work.

A computer virus is one type of malware that inserts its virus code to multiply itself by altering the programs and applications.

The computer gets infected through the replication of malicious code.

Computer viruses come in different forms to infect the system in different ways. Some of the most common viruses are

Boot Sector Virus – This type of virus infects the master boot record and it is challenging and a complex task to remove this virus and often requires the system to be formatted. Mostly it spreads through removable media.

Direct Action Virus – This is also called non-resident virus, it gets installed or stays hidden in the computer memory. It stays attached to the specific type of files that it infect. It does not affect the user experience and system’s performance.

esident Virus – Unlike direct action viruses, resident viruses get installed on the computer. It is difficult to identify the virus and it is even difficult to remove a resident virus.

Multipartite Virus – This type of virus spreads through multiple ways. It infects both the boot sector and executable files at the same time.

Polymorphic Virus – These type of viruses are difficult to identify with a traditional anti-virus program. This is because the polymorphic viruses alters its signature pattern whenever it replicates.

Overwrite Virus – This type of virus deletes all the files that it infects. The only possible mechanism to remove is to delete the infected files and the end-user has to lose all the contents in it.

Identifying the overwrite virus is difficult as it spreads through emails.

Spacefiller Virus – This is also called “Cavity Viruses”.

This is called so as they fill up the empty spaces between the code and hence does not cause any damage to the file.

Few file infector viruses come attached with program files, such as .com or .exe files. Some file infector viruses infect any program for which execution is requested, including .sys, .ovl, .prg,

mnu files. Consequently, when the particular program is loaded, the virus is also loaded.

Besides these, the other file infector viruses come as a completely included program or script sent in email attachments.

As the name suggests, the macro viruses particularly target macro language commands in applications like Microsoft Word.

The same is implied on other programs too.