Computer Virus

A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.

How do I know if a virus has infected my computer?

Your computer runs slower than normal

Your computer stops responding or locks up often

Your computer crashes and restarts every few minutes

Your computer restarts on its own and then fails to run normally

Applications on your computer do not work correctly

Example of a Computer Virus - The "I Love You" Virus

This is not the reason that the "I Love You" virus came into being. The author of this particular virus was a computer student in a college in the Philippines and wrote the virus as an experiment, not intending it to ever be used. The virus was obtained by someone close to her and released into the wild and had infected millions of computers worldwide in a few hours! This particular virus attacked media files like JPGs and MP3s and for each one on a PC, it became a part of the virus, spreading it across the world like an ill-wind.

The "I Love You" menace clogged up Web servers, manipulated personal files and caused IT System Managers to shut e-mail systems off the network. (The author was one of these IT Managers - we saw the email proliferating and as fast as we shut subsystems down, the faster the menace came flooding inwards. In the end, we had to completely shut the network off from the outside world.

How It Appears
Arriving in your e-mail with a subject line: "I Love You" and including an attachment entitled "Love-Letter-For-You.txt.vbs," this is supposed to be a real lure(!) but you (now) know better! Opening the attachment obviously infects the computer. But with a modern virus-checker like [Alwil Avast! Home Edition] home users can protect themselves from ever getting near to a menace like this, since the virus checker will catch it before it can ever be opened.

On with the story (since this is just a story really!): once the computer has been infected the virus does its work like this: first it scans the memory for passwords, and these would be sent back to the virus creator's web site which will never happen because it has long since been shut down. Then the infection replicates itself to all addresses found in any Outlook address book on the machine. Last of all, it corrupts files with extensions ending with .vbs, .vbe, .js, .css, .wsh, .sct, .hta, .jpg, .jpeg, .mp2, .mp3 by overwriting them with a copy of itself.

This is an old virus, (1995 or so) but demonstrates what viruses do to a computer and the danger of the "classic" self-replicating behavior which first started in the mid 90s.