Prevention is better than cure in protecting your computer from invaders

PUBLISHED : Wednesday, 24 October, 2001, 12:00am
UPDATED : Wednesday, 24 October, 2001, 12:00am

AS COMPUTERS have become a necessity, the threat from viruses should not be neglected. Computer viruses can affect a system's operation or cause disastrous and extensive data corruption. Prevention is better than cure, so it is important to learn how to detect viruses.

Like a biological virus, a computer virus needs a host so that it can reproduce itself. A virus is transmitted between hosts and can damage them.

Since the first computer virus was found in 1986, the total number has kept growing to around 50,000 today.

They can be classified into four main types depending on how they are transmitted: boot sector; file or program; macro; and multipartie. A boot sector virus is transmitted when an infected floppy disk is left in a computer drive and the system is re-booted. The virus from the infected disk is transferred to the system's hard drive master boot record. The master boot section is the first place that the system reads from when booting up.

File or program viruses are pieces of code that attach themselves to executable programs. Once the infected program is run, the virus is transferred to the system's memory and may replicate itself there.

Macro viruses are the most common type. They infect files run by applications that use macro languages, such as Microsoft Word or Excel. When the file is opened, the virus can execute commands using the macro language. Usually, macros are used to automate tasks and customise user settings. Macro viruses typically infect global setting files such as Word templates so that subsequently documents are contaminated with the infected code.

Multipartie viruses are hybrids of boot sector and file viruses. They can breed in the boot sector and transmit via files run by applications or vice versa.

A computer infected with a virus shows symptoms such as unusual messages or displays on the screen; unusual sounds or music played at random times; having less available memory than it should; a disk or file name being changed; programs or files suddenly going missing; unknown programs or files being created; files suddenly not working or becoming corrupted.

Preventing virus infections does not require much time and effort.

?Do not open any files attached to an e-mail from an unknown, suspicious or untrustworthy source.

?Delete chain and junk e-mail. Do not forward or reply to any of them. These 'spam' e-mail are unsolicited and intrusive and clog up the network.

?Do not use illegal software.

?Back up your files regularly. If a virus destroys your files, at least you can replace them with back-up copies.

?Exercise caution when downloading files from the Internet. Ensure that the source is a legitimate and reputable one. Verify that an anti-virus program checks the files on the download site. If you are in doubt, do not download the file or download it to a floppy and test it with your own anti-virus software.

There are also free anti-virus programs to protect and scan the computer viruses on these Web sites:,, and

A computer infected with a virus shows symptoms such as unusual messages or displays on the screen