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Computer Virii

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Introduction

When things go wrong Virus Viruses and errors are common in the ICT world. They are essential to understand and know how to deal with them. A properly engineered virus can have an amazing effect on the Internet or on a network of some type. Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person. A computer virus must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents. Early viruses were pieces of code attached to a common program like a popular game or a popular word processor. A person might download an infected game from a bulletin board and run it. A virus like this is a small piece of code embedded in a larger, legitimate program. Any virus is designed so it runs first when the legitimate program gets executed. ...read more.

Middle

The trigger might be a specific date, or the number of times the virus has been replicated, or something similar. In general, most viruses are not very threatening any more. The first reason for the decline has been the huge size of today's programs. Nearly every program you buy today comes on a compact disc (CD). Compact discs cannot be modified, and that makes viral infection of a CD impossible. The programs are so big that the only easy way to move them around is to buy the CD. People don't carry applications around on a floppy disk like they used to, when floppy disks were the main way of transferring information and programs The latest thing is the e-mail virus, and the Melissa virus in March of 1999 was spectacular. Melissa spread in Microsoft Word documents sent via e-mail, and it worked like this. Someone created the virus as a Word document uploaded to an Internet newsgroup. Anyone who downloaded the document and opened it would trigger the virus. The virus would then send the document (and therefore itself) ...read more.

Conclusion

It also has a useful but dangerous auto-execute feature. A programmer can insert a program into a document that runs instantly whenever the document is opened. This is how the Melissa virus was programmed. Anyone who opened a document infected with Melissa would immediately activate the virus. It would send the 50 e-mails, and then infect a central file called NORMAL.DOT so that any file saved later would also contain the virus! It created a huge mess. Microsoft applications have a feature called Macro Virus Protection built in to them to prevent this sort of thing. If you turn Macro Virus Protection on, then the auto-execute feature is disabled. By default the option is ON. So when a document tries to auto-execute viral code, a dialog pops up warning the user. Unfortunately, many people don't know what macros or macro viruses are, and when they see the dialog they ignore it. So the virus runs anyway. Many other people turn off the protection mechanism. So the Melissa virus spread despite the safeguards in place to prevent it. In the case of the ILOVEYOU virus, the whole thing was human-powered. If a person double-clicked on the program that came as an attachment, then the program ran and did its thing. ...read more.

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