COMPUTER VIRUSES

Defn: A Computer Virus is a program that infects computer files and makes them do something unexpected or damaging.

How does it work?

A copy of the virus program is usually inserted into a computer file and when the file is used, it is first loaded into memory (RAM) after which other files become infected

How are viruses spread?

1. Sending infected files via e-mail

2. From a Diskette or USB Flash Drive containing an infected file

3. Downloading programs and files from the Internet

4. Infected CD-ROMs

TYPES OF VIRUSES 

1. Those that infect program files - the virus code is attached to program files and when the program is loaded, the virus is loaded as well. 

2. Those that infect system or boot files - the boot file is a small program that tells the computer how to load the rest of  the operating

system. When this file gets infected, the virus is loaded into memory and is able to run when the computer is on.

3. Macro Viruses - these are written in a macro language which is associated with an application such a Microsoft Word.  The macro virus is 

carried by a document file and is executed when the document is opened.  Over half of the known viruses are macro viruses spread by

e-mail attachments.

PREVENTING VIRUSES

1. Install anti-virus software such as: Norton, McAfee, AVG, Avast etc.

2. Turn on program virus protection

3. Try to know the origin of each program or file you use

4. Never open an e-mail with an attachment which contains file extensions such as EXE, COM, VBS etc.

WHAT IS A WORM? 

Defn: A worm is another electronic threat.  Unlike a virus, it does not require a host program in order to be transmitted.

Worms can be transmitted via e-mail and are capable of copying themselves into memory.  Mass mailing worms can create infected e-mail messages and send them to addresses saved on the infected computer.  An example include  w32/netsk.b@mm is a mass mailing worm which e-mails itself to addresses and tries to copy itself onto networks.