Whenever our computer behaves strangely, the first thing that we suspect is that a virus has infected our PC. If your computer is connected to the Internet then most probably your suspicion will turn out to be true.
But virus is just one of the forms of intrusion. Computer intrusions can take several forms, including viruses, worms, and Trojan horses. I am sure you have heard of them though you may not know what they are and how they differ. Here is a brief look at each of them.
Viruses are snippets of software code that are usually delivered hidden inside another apparently innocuous program or data file. When you open the file that contains a virus, the virus program runs and does whatever damage it was designed to do. Many viruses also attach copies of themselves to other programs or data files so that they can spread to other computers, just like biological virus spreads from person to person.
An e-mail virus is embedded inside an e-mail message. When recipients open infected messages, the virus runs on their computers and also sends copies of itself to e-mail addresses in the recipients’ address books.
A worm is software that is designed to take advantage of security problems in widely used programs (often e-mail programs). The worm distributes itself from computer to computer through the Internet and across other computer networks. Many worms also do other damage, such as replacing web pages on infected servers with content created by the worm’s originator. Worms can also direct massive attacks on specific computers (computers at the White House and Microsoft are popular targers) in order to overload and crash their Internet access.
A Trojan horse is a program in disguise. For example, it may be identified as a
downloadable game or music file, but when it is opened, it’s actually something else entirely. That something else usually does some kind of damage, such as erasing the contents of a hard drive or forwarding data to another computer through the Internet.
Most of the modern Anti-Virus programs battle against all of the above three. But remember to keep your virus definitions updated regularly. If you do not have an Anti-Virus installed, the best option is to get your computer scanned online with applications like Panda ActiveScan.