Performance objectives Students should be able to:
1. State the meaning of computer virus
2. State types of computer viruses
3. List examples of computer viruses
4. State sources through which computers can be infected with viruses
5. State warning signs of a virus 6. List anti-virus software available
UNIT ONE: COMPUTER VIRUS
14.1. MEANING OF A COMPUTER VIRUS
Computer viruses are electronic materials that cause problems to computers. They can be likened to parasites that cause disease in man.
Figure 118: Computer virus destroys computer
14.2. TYPES OF COMPUTER VIRUS
There are different types of computer viruses. However, the most common types are:
14.2.1. BOOT VIRUSES
14.2.2. PROGRAM VIRUSES
14.2.3. MACRO VIRUSES
14.2.1. BOOT VIRUSES
Boot viruses are the group of viruses that infect the part of the computer that controls the process of booting of the computer such as ROM and BIOS. Examples of boot viruses are Disk Killer, and Stone virus.
14.2.2. PROGRAM VIRUSES
Program viruses are group of viruses that infect executable program files, such as those with extensions like .BIN, .COM, .EXE, .DRV (driver) and .SYS. Examples of program viruses are Sunday, Cascade virus.
14.2.3. MACRO VIRUSES
Macro virus is the type of computer virus that infects the macros within a document or template. When you open a word processing or spreadsheet document, the macro virus is activated and it infects the Normal template (Normal.dot)-a general purpose file that stores default document formatting settings. Examples of macro viruses are DMV, Nuclear, Word Concept virus
14.3. SYMPTOMS OF VIRUS INFECTION
Symptoms are the abnormal behaviors or signs that appear on your computer or your computer exhibits. These signs or behaviors tell you that your computer is attacked by a virus or worm. For instance, if a computer is attacked by a virus, a warning sign as in the picture below will appear on your desk top (if you are using AVG Antivirus Software). Some of the major signs of virus attack and destruction are:
- Your computer will be slow
- Your computer stops responding to commands
- Your computer crashes and restarts every few minutes
- Disks or disk drives are inaccessible
- You can't print correctly
- You see unusual error messages
- You see distorted menus and dialog boxes
- Programs take longer to load.
- Strange characters appear in the directory listing of filenames.
- Strange graphic displays such as falling letters or a bouncing ball appear on screen.
- Programs may hang the computer or not work at all.
14.4. SOURCES OF COMPUTER VIRUS
Some of the most important sources of viral infection are:
14.4.1. INFECTED DISKETTES, CD-ROMS
14.4.2. E-MAILS
14.4.3. INTERNET DOWNLOADS
14.4.4. ILLEGAL DUPLICATION OF SOFTWARES ETC