Virus

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 * Computer viruses** are manmade and are in forms of codes which are loaded into the computer without any prior warnings from sources such as an email attachment or free softwares downloaded from p2p networks. A virus is also a self-replicating program that spreads throughout the computer system within seconds after it is inserted into the computer. It is also referred to as //worms//, //trojan horses// or other types of malwares. Viruses are threatning for the computer system, even very minor viruses can bring the system to a halt.

According to [|Wikipedia], there are categories of viruses such as some can be very destructive and some can be very annoying. Viruses also takes effect at different time periods. For example, if the virus delays the destruction, it is refered to as a //bomb//. Secondly, a //time bomb// occurs during a specified time or date. Lastly, the //logic bomb// which takes effect after the user triggers it. (wikipedia)

=Difference between a Virus, Worm, and a Trojan Horse=

Viruses

 * Viruses** are usually attached to a program, file or an email and are sent by the creators of virus to regular users. As the virus travels to different users, it damages the data on your computer. Some viruses cause minor damages but some does severe damages such as damages to your hardware, software, files, and data. Since the virus is sent through attachements, a user has to open the file in order for the action to take place, or else the virus is inactive. If the infected computer sends other users the same file, it is likely that the virus will travel and spread all over.

Worms
A **worm** is a sub-category of a virus. It also travels from computer to computer without the help of people. Worms usually infect files or information transport features and transfers unaided. First of all, a worm can replicate itself as many times as it likes, send the virus to itself again and grow in number. Secondly, a worm is also capable of sending the virus to other people through email or file transfers (through programs such as MSN messenger) that are sent to the users friends without the user knowing.

For example, on msn, **//Person A//** receives a message from **//Person B//** requesting //Person A// to accept an awesome file named **hallo.** As soon as //Person A// accepts this file and opens it, the computer freezes and shuts down.

//Person A// restarts the computer and asks //Person B//, **"What did you send me?**" and //Person B// says "**Nothing. I didn't even message you."**

Worms basically spread on its own, messages your own friends, emails all the contacts on the users list without any persmission or any prior notification.

Trojan Horses
A **trojan horse** looks like a useful software but once a user runs it on their computer system, it will cause damage. When users receive this file, they think this software is from a legitimate source but usually Trojan Horse can damage all important data or just change the desktop appearance to annoy the users. The worst aspect of the Trojan Horse is the fact that it has a backdoor to which a malacious user can control the whole system from anywhere they like.

=**Protection from Viruses**=

//In order to protect the computer system from dangerous viruses, users should always://
 * Install Anti Virus Software to check emails and attachments from viruses.
 * It is necessary to always update the software for new warnings on viruses.
 * And be behind a firewall.