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Viruses

First, don't worry unnecessarily but do not ignore the problem. Before you start, as a general precaution, always scan your floppy + zip diskette. There are many different kinds of viruses, but basically a computer virus is a program and as such must be run OR opened in order to unleash its intended function. Not all viruses are destructive, but some are extremely destructive, and luckily, rare. Some viruses may be attached to a legitimate program, some are made such that their file name looks like a legitimate program, and some may even be macros that run in Microsoft Word or Excel. In any case the simple act of downloading the file will not unleash the virus. Only the act of running or opening the program / file will cause the virus to do its thing.

What is a computer Virus?

A computer virus is a hidden program that invades your computer, much like a biological virus invades a living cell. A computer virus contains hidden code which performs some usually unwanted function to a computer without your permission or knowledge. You can think of a virus as a time bomb, waiting to explode at any time it is set to so by the author of the virus.

How does a virus Work

A computer virus performs two basic functions: it copies itself from machine to machine (self-reproducing), and it executes the instructions the perpetrator has planned. A computer virus exhibits three characteristics: a replication mechanism, an activation mechanism and an objective.

The replication mechanism searches for other programs to infect, if it finds any, it inserts the hidden instructions in the program then it modifies the execution sequence of the program's instructions such that the hidden code will be executed whenever the program is invoked. The activation mechanism checks for the occurrence of some event. When the event occurs, the computer virus executes its objective.

What damage can a virus do?

A computer virus is one kind of threat to the security and integrity of computer systems. Like other threats, a computer virus can cause the loss or alteration of programs or data. The damage done depends on the computer virus, and there is a range of possibilities: There are viruses that do basically no damage, all the way up to the viruses that can completely destroy your files or make your machine unusable.

How many Viruses are there?

Computer viruses have impacted a significant number of computers over the past few years. There are currently over 9000 known computer viruses worldwide. Over 200 new viruses are being discovered every month.

Computer viruses should always be taken seriously. If these viruses are left undetected, they may result in directory damage, memory limitations and hard disk reformatting, and could therefore cause loss of data and programs. However, some of these viruses are harmful and some are known as Virus Hoaxes that have been spreading over the Internet and via e-mail.

How do they spread?

Viruses spread by disks or programs swapped with other people, freeware or shareware downloaded from bulletin boards, pirated copies of software and even from purchased software from publishers.

What are the symptoms and indications of a Computer Virus infection?

Some computer viruses alert you to their presence by putting an unexpected message on your screen. Some characteristics you should be encouraged to watch for include: programs taking longer to start, or running more slowly than usual, disk accesses seem excessive for simple tasks, access lights turned on for non referenced devices, unexplained decreases in the amount of available memory, programs of files mysteriously disappear, a sudden reduction in disk space, executable files change size and unexplained hidden files present.

Please note that most computer problems are not caused by viruses. It is also important to remember that future viruses may behave differently. You should be alert to unexpected behavior on your computer.

How do I check my computer or diskette for Viruses and how do I remove a virus?

You need to use a virus scanning program to check your computer or diskette for viruses. There are a number of companies that are in the business of providing virus scanning programs and anti-virus removal software, such as Norton AntiVirus.You can scan your floppy diskettes Zip disks for known viruses and also disinfect systems with viruses.

It is strongly recommended that you check your diskettes and Zip disks periodically for viruses.

Removing file Viruses: Using anti-virus software designed for cleaning is convenient, and is usually safe enough, but there is no guarantee that files will be restored to their original condition. Many viruses are poorly written, and damage files that they infect. Replacing infected files with uninfected backups is preferred.

Should you Format a diskette to clean Viruses?

That's a personal choice, but only in cases where a file-infecting virus has spread extensively, so that formatting the disk might be the quickest solution. However, formatting should be a last resort, done only if a current backup exists, made before the infection began. Almost all the time, removing a virus and getting the system back to normal is more involved than simply deleting a file, but less burdensome than deleting everything, which the Format command will do.

When not to Format

Formatting may not be a wise idea, if the backup is also likely to be infected, or if it is incomplete. More people have lost data from rash use of the Format command than from viruses.

Screen Savers

It is recommended that Screen Savers are NOT brought in from the Internet as these may contain viruses



Department of computer science and information systems
University of limerick, limerick, Republic of Ireland

Department of Computer Science and Information Systems, University of Limerick, Limerick, Republic of Ireland
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