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Aug 24
2008

Difference between Virus, Worm and Trojan Horse

Posted by SHENGTON in Untagged 

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Virus --> Like a biological virus, a computer virus is something you don't want to get. Computer viruses are small programs or scripts that can negatively affect the health of your computer. These malicious little programs can create files, move files, erase files, consume your computer's memory, and cause your computer not to function correctly. Some viruses can duplicate themselves, attach themselves to programs, and travel across networks. In fact opening an infected e-mail attachment is the most common way to get a virus.

We all know it's hard enough to get a computer to work well when it is healthy, let alone when it has been attacked by a virus. Therefore, it is better to prevent an attack than to try and cure it. There are many anti-virus programs available that scan incoming files for viruses before they can cause damage to your computer. Some of these programs include Norton AntiVirus?, McAfee VirusScan?, and Virex?. It is a good idea to have one of these programs on your computer to prevent a virus attack. It is also important to update your virus definitions file at least once a month so that your anti-virus program can check for all the latest viruses. It's a lot like having a glass of orange juice every morning -- it keeps your computer's immune system strong and healthy.

Worm --> has two widely different definitions. One refers to a computer virus and the other is an optical storage technology:

1) A type of computer virus

Just like regular worms tunnel through dirt and soil, computer worms tunnel through your computer's memory and hard drive. A computer worm is a type of virus that replicates itself, but does not alter any files on your machine. However, worms can still cause havoc by multiplying so many times that they take up all your computer's available memory or hard disk space. If a worm consumes your memory, your computer will run very slowly and possibly even crash. If the worm affects your hard disk space, your computer will take a long time to access files and you will not be able to save or create new files until the worm has been eradicated.

Worms are hard to detect because they are typically invisible files. They often go unnoticed until your computer begins to slow down or starts having other problems. Unlike viruses and Trojan horses, worms can replicate themselves and travel between systems without any action from the user. For these reasons, it is good to have an antivirus program installed on your system that can detect and remove worms before they have a chance to replicate or spread to other computers. Security updates such as Windows Update also patch security holes that allow worms to infect your computer. So keep your security updates and virus definitions up-to-date and you should be able to keep your computer worm-free.

2) An optical storage technology

WORM can also mean "Write Once, Read Many." It is an optical storage technology that allows a disc to be written only once but read an unlimited number of times. WORM devices were introduced in the 1970's and gained popularity as a way of archiving data. The storage capacity of WORM discs began around 140MB, but increased to more than 3.0GB over the past few decades. Yet the WORM technology has no standard format, so WORM discs are only compatible with the drives that wrote them. This limitation has kept WORM equipment relatively expensive and has kept the technology from gaining widespread acceptance.

Today, most optical drives are based on either CD-R or DVD-R technology. Unlike WORM discs, CD-Rs and DVD-Rs can typically be read by any CD or DVD drive, regardless of the manufacturer. Because of their improved compatibility and lower costs, writable CDs and DVDs have all but replaced WORM media.

Trojan Horse -->
In Greek mythology, there is a story about the Trojan War. This war lasted many years, as the Greeks could not penetrate the heavily barricaded city of Troy. So one day, a few of the Greek soldiers brought the people of Troy a large wooden horse, which they accepted as a peace offering. The horse was moved inside the city walls, where it sat until the night. After the people of the city had fallen asleep, Greek soldiers jumped out of the wooden horse, opened the gates to let their fellow soldiers in, and took over the city.

So what is the moral of this story? Mainly, beware of Trojan horses. But how does that relate to computers? That's a good question. In the computing world, Trojan horses are more than just a myth. They really exist and can cause damage to your computer. Trojan horses are software programs that masquerade as regular programs, such as games, disk utilities, and even antivirus programs. But if they are run, these programs can do malicious things to your computer.

For example, a Trojan horse might appear to be a computer game, but once you double-click it, the program starts writing over certain parts of your hard drive, corrupting your data. While this is certainly something you want to avoid, it is good to know that these malicious programs are only dangerous if they are given a chance to run. Also, most antivirus programs can catch Trojan horses when scanning for viruses. Unlike viruses, however, Trojan horses don't replicate themselves. Though it is possible for a Trojan horse to be attached to a virus file that spreads to multiple computers.

So as a general rule, don't open a program unless you know it is legitimate. This applies especially to e-mail attachments that are executable files. Even if you are pretty sure the attachment is OK, it is still a good idea to run it through your virus scan program (with the latest virus definitions) just to be safe. Remember what happened to the people of Troy -- don't let a Trojan horse catch you off guard.

Source --> HERE

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