Now and again, we hear of statements like, “My computer has been hit by a virus” or “The data has been chewed by a virus”, etc.
What is a virus in computer terms after all? A computer virus (like its kin), is a small piece of software or can we call it program that disorganizes or distorts the way a computer works; by disguising itself as a normal program. E.g, a virus might attach itself to a program such as a word file, an MP3 musical file, a photographic item, etc.
Each time the host program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or inflict mayhem.
Viruses are of several categories like, e-mail viruses, Trojan horses, worms etc.
An e-mail virus embeds itself on to an email message attachment, and usually replicates itself by automatically mailing itself to several people in the victim’s e-mail address book.
Some e-mail viruses don’t even require to be opened; they launch when you view the infected message in the preview pane of your e-mail software and can be passed on effortlessly without any suspicion that one is doing so.
A Trojan horse is simply a computer program that claims to do one thing (it may claim to be a game) but instead
does damage when you run it (it may erase your hard disk).
Trojan horses have no way to replicate automatically.
These derived their name from the “Trojan of Troy”, where soldiers were hidden inside a huge Trojan horse, the horse was dragged into the city of Troy by unsuspecting Troy soldiers, as they slept at night, their adversaries in the Trojan horse sneaked out and wrecked mayhem on their “hosts”.
On the other hand, a worm is a small piece of software that uses computer networks and security holes to duplicate itself.
A copy of the worm scans the network for another machine that has similar security vulnerability.
It copies itself to the new machine using the security hole, and then starts doing the same from there, as well.
It is strange; the computer virus is something of an Information Age wonder.
The computer viruses show us how vulnerable we are, a properly engineered virus can have an overwhelming effect, disrupting productivity and causing several millions if not billions of dollars in damages.
It is estimated that the “Mydoom worm” infected almost a quarter of a million computers in a single day in January 2004.
Mayhem was in March 1999 when the “Melissa virus” was so powerful that it forced Microsoft and a number of other very large companies to completely turn off their e-mail systems until the virus could be contained.
The “ILOVEYOU virus” in 2000 had a similarly devastating effect.
In January 2007, a worm called “Storm” struck and by October, it is believed that, up to 50 million computers were hit.