Viruses : Spread

A computer "catches" a virus when a floppy disk or CD-ROM containing a virus is used on the computer. The virus may be hidden at the start of the disk or CD-ROM (in the "Boot Sector") or may be hidden inside another file.

When you access the disk or CD-ROM the virus will copy itself onto your hard disk. It will do this by looking for another program on your hard disk and attaching itself to this program. The virus may make lots of copies of itself, adding itself on to the end of other files on your hard disk to hide itself. The more copies of the virus that are made the harder it will be to get rid of.

Viruses can also be caught from files loaded across a network such as a school network or the Internet. In particular a number of recent viruses have been transmitted as files attached to emails. Viruses which attach themselves to emails can spread much more quickly that viruses which spread by other methods.

A virus only spreads when the user of a computer does something such as opening a file or reading an email. Worms spread across a network without the user doing anything. They simply look for computers connected to the network and copy themselves onto these.

GCSE ICT Companion 04 - (C) P Meakin 2004