Prevention is better than cure in protecting your computer from invaders

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.