Trojan Horses, Worms and Viruses are harmful programs that could cause damage to the computer and the information on the computer. They can even slow down your Internet, and they could even use the computer to spread by themselves to your co-workers, family, and friends and to rest of the Web.

What is a virus?

A virus is a small piece of computer code that gets itself into a file or program so that it can spread from one computer to the other. It goes on infecting as it travels. Viruses could damage your files, your hardware and your software.

Virus (n.) A Code written with an express intention to replicate and manipulate itself. A virus gets itself to the host program and then tries to spread from one computer to the other. It could damage the information, software or the hardware.

Just as the human viruses, the computer viruses too range from mildly bothersome to downright destructive. But the good news is that the true virus won't spread without the human action. Someone has to send an e-mail or share a file to keep it moving.

What is a worm?

A worm, like the virus, is fashioned to copy itself from a computer to another, but it does this automatically.  Firstly, it takes control of the features on a computer that can transport the information of the files. Once the worm is in the system, it can propagate alone. The great danger of the worms is the capability of replication in huge volume. For instance, a worm can send out the copies of itself to almost everyone listed in the address book of the e-mail, and their computers too would do the same leading to the domino effect of huge network traffic which can slow down the Internet and the business networks as a whole. When the new worms are revealed, they spread very soon. They clog the networks and possibly make you to wait for a long time to view the Web pages.

Worm (n.) is a subclass of the virus. A worm usually spreads without the user action and replicate complete copies of itself across the networks. A worm can eat away the network bandwidth or memory, which might cause the computer to crash. Recent examples of the worms include the Blaster worm and the Sasser worm

What is a Trojan horse?

Trojan horses are the computer programs which appear as the useful software, but rather they compromise the security and cause huge damage. The recent Trojan horse arrived in the form of the e-mail which included the attachments that claimed themselves to be the security updates from the Microsoft, but instead turned out as the viruses which attempted to incapacitate the firewall and antivirus software.

Trojan horse (n.) is a computer program which appears to be an useful utility but actually does a damage.

Spyware