What is a ‘Virus’?How Does a Virus Work?

What is a ‘Virus’?

A computer virus is a program or piece of code that operates by attaching itself to some other program or downloaded file. When this program starts, the virus code unintentionally runs, replicates itself and infects other programs or documents on the PC. A computer virus spreads mainly via e-mail attachments, downloadable files from the Internet or floppy disks. Virus infection can be prevented by installing (and maintaining) anti-virus software, among other strategies, some of which are outlined in this advice sheet. A computer virus can seriously damage or completely destroy files or software on a computer. The result is that files may be lost permanently, educational programs may not function correctly or the overall performance of a computer may be slowed down. The process involved in repairing the damage can be time consuming and expensive.

How Does a Virus Work? 

There are two ways in which a virus behaves when activated. 

      •  Direct Action – the virus is activated immediately, frequently relying on other 

         programs to infect and carry out specific behaviour encoded by the author of the 

         virus. 

      • Memory Resident – the virus is loaded into the computer’s memory and is activated 

     by a triggering event. A triggering event can be either a date or a certain combination 

       of keystrokes. 

The damage caused by computer viruses varies from poor computer performance to erasing the hard drive. 

Preventing Virus Infection :

• Install and regularly update anti-virus software. This, in conjunction with good 

housekeeping, can greatly reduce the threat caused by computer viruses. 

• All floppy disks or other removal media, should remain within the confines of the 

computer room. It is not advisable to let students bring them home or return with them 

to school. However, if this occurs they should be scanned immediately using antivirus software. Floppies should also be write-protected. 

• Files should be saved to a designated hard drive where incoming files can be 

scanned automatically by anti-virus software. 

• When the sender of an e-mail is not known to the recipient, avoid clicking on 

attachments containing an executable file. 

• Creating back-ups of files won’t directly prevent virus infection, but it may speed up 

the recovery process in the event of a virus erasing or damaging files. 

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