What is a virus?
A computer virus is a package of computer code that infects a computer. It can be distributed through infected floppy disks and CDs, via e-mail and the Internet. Some viruses are relatively harmless and cause minor inconvenience, for example, they might cause a message to pop up on your screen. However, other viruses are far more damaging and can prevent users logging on to their computers, cause data loss, damage programs and even wipe your hard drive. A virus must meet the following criteria:
- It must be able to execute itself
- It must be able to replicate itself
There are five known types of computer virus:
1. Boot sector virus: floppy and hard disks contain a small area that is used when your computer loads up. A boot sector virus will infect your computer and overwrite these areas preventing you from accessing your computer.
2. File infector viruses: these viruses infect program files with .com and .exe extensions preventing you from running programs installed on your computer. The virus is memory resident and will infect all program files on your hard drive when they are run.
3. Macro viruses: these are the most common and easy to create viruses in circulation. The majority are designed to exploit Macro functions in Microsoft® Word, Excel and Access, however, other programs are now coming under target. These viruses infect your data files and have proven very expensive for businesses in terms of lost files and the time taken to clean up the damage.
4. Master boot record viruses: these infect a computer in the same way as boot sector virus. The Master Boot Record (MBR) tells your computer how to load the operating system. The virus will normally overwrite this and save a copy of the original file in a different location.
5. Multi-partite viruses: these viruses infect both program files and boot records. They are notoriously difficult to clean because if you manage to clean one and not the other then your computer will become re-infected.
What is a Trojan?
A Trojan is a file that pretends to be something legitimate on your computer. Once it is run it can destroy or leak your personal files to an outside source. Unlike a virus these cannot replicate or run themselves. Normally you can become infected through opening an infected email attachment or downloading an infected file from floppy disk, CD or the Internet.
What is a worm?
Worms are programs that spread from system to system and are able to replicate themselves without the need for an infected host file. Worms normally reside in Word or Excel files. Once on a system they will release an infected document onto that system. When the file is copied this in turn releases an infected file onto the new system.
Protecting yourself from infection
It is a fact that all computer users will become infected with a virus at some point. But you can take steps to minimise the risk and reduce the damage a successful infection can cause. How? By installing an Anti-virus program.
There are a number of programs available to buy, there are even some free programs on the Internet. If you bought a computer from a store you may even have been supplied with an anti-virus program as part of the software package.
Tips for preventing virus infections
- Install anti-virus software. You can buy this from any computer store.
- Keep your software updated: anti-virus software normally comes with a period of free updates which ranges from 3 to 12 months. You will need an Internet connection to install the updates. Try to do this every few days.
- Only download files from a trusted website.
- Disable the preview pane in your email program. Many viruses will exploit this feature.
- Only load files from floppy disks and CDs from a trusted source.
- Don’t open emails from people you don’t know, especially if it has an attachment.
- Be careful when using peer to peer file sharing software, the file you are downloading may be infected.
