This document discusses computer viruses, including their symptoms, how they spread, types of viruses, and prevention methods. A computer virus is a program that replicates itself and damages computer files and memory. Viruses can slow computer performance, reduce available memory, and cause data loss. They spread through email attachments, downloads, removable drives, and infected computers. There are different types like boot sector viruses and Trojans. The document recommends installing antivirus software, regularly updating it, avoiding unknown file sources, and only downloading software from trusted sources to prevent virus infections.

1. Computer Viruses
Name:-CUSSON NGWENYA

2. Presentation
 Introduction
 Symptoms
 How does it spread
 Types of Computer Viruses
 Prevention Methods
 Antivirus Programs

3. Introduction
 A computer virus is a program which replicates
itself, damages or corrupts files and memory of
the computer, for example, a Trojan horse. By
replication, it means that the virus can multiply
itself (produces several similar copies of itself)
when it enters the computer system.

4. Signs and symptoms of virus attack on a
computer
 Reduced system performance (reduced speed
of operation)
 The size of available free memory
reduces.
 Unexplained and frequent lose of data
held in the computer
 The computer fails to boot.
 The hard disk becomes inaccessible (the
user cannot access data held in the
computer)

5. Effects of computer viruses
 Memory of a computer will be used up, slows down
computer.
 Alters system settings.
 Erases and corrupts files and data on the computer.
 Infects other computers on network.
 Leads to production loss.
 Leads to financial loss.
 The computer fails to boot.
 The computer system produces wrong results of a
process.

6. How does it spread
 Can come as e-mail attachments
 Can come with downloads from bulletin boards
 Computer viruses spread by attaching themselves
to other computer program files.
 When you exchange a file or pen drive with a virus,
the virus spreads from one computer to the
another.
 Viruses also spreads when a Computer Engineer
comes to repair your system and puts his/her
diagnostics disks in your PC

7. Types of computer viruses
 Boot sector Viruses- These viruses affect
the booting sector on the hard disk so
that the computer fails to boot.
 Time bomb- Virus attack and destroys
computer files at a specific date and
time
 Logic bombs -A type of virus that attacks
the computer when a specific event
occurs and destroys everything on the
computer disk like the Friday the 13th

8. Types of computer viruses
(cont’d)
 Trojan Horse virus -These are viruses that appears as
programs useful to the user with the intention of soliciting
information like user accounts and passwords or damaging
computer system files.
 WORM viruses -A program capable of reproducing itself and
spread from one computer to the next over a network and
damage computer files.
 File sector Viruses -These viruses destroy files that are
created by users on the computer.

9. Methods of prevention
 Install an Antivirus software
 Regularly update the program
 Do not open file attachments from unknown
sources or download doubtful software from
the Internet. Do not use files that come from
unknown sources.
 Buy original software and do not buy pirated
software
 Open email attachment files only if you are
expecting the attached files, or the sender is
known and has confirmed sending the file
 Try to avoid downloading and installing
software from the Internet

10. Antivirus Programs
 Avg
 Avira
 Norton Anti-Virus
 MaCfee
 Avast
 Panda
These are programs that detect computer viruses and reduce
the risk of computers being attacked by viruses for example

11. Thank You