Computer Virus

Definition of

Computer

Virus

▪ A computer virus is a small software program that

interferes with computer operation and spreads from one
computer to another.

▪ A virus is a self-replicating program that copies itself and

that can infect other programs by modifying them or their
environment such that a call to an infected program
implies a call to a virus

▪ Computer viruses are executable computer programs

written by software developers to check piracy on some of
their system and application software.

Types of
Computer

Viruses

BOOT SECTOR VIRUS

▪ This type of virus infects the master boot record. It is

challenging and a complex task to remove this virus and
often requires the system to be formatted. Mostly it
spreads through removable media.

DIRECT ACTION VIRUS

▪ This is also called a non-resident virus, when executed

scans the disks for targets, infects them, and then exits
(i.e. it does not remain in the memory after it is done
executing).

RESIDENT VIRUS

▪ Resident virus installs itself as part of the operating

system when executed, after which it remains in the RAM
from the time the computer is booted up to when it is shut
down

MULTIPARTITE VIRUS

▪ This type of virus spreads in multiple ways. It infects both

the boot sector and executable files at the same time

POLYMORPHIC VIRUS

▪ These types of viruses are difficult to identify with a

traditional anti-virus program. This is because
polymorphic viruses alter their signature pattern
whenever it replicates.

OVERWRITE VIRUS

▪ This type of virus deletes all the files that it infects. The

only possible mechanism to remove is to delete the
infected files and the end-user has to lose all the contents
in it. Identifying the overwrite virus is difficult as it spreads
through emails.

SPACE FILLER VIRUS

▪ This is also called “Cavity Viruses”. This is called so as

they fill up the empty spaces between the codes and
hence do not cause any damage to the file.

MACRO VIRUSES

▪ As the name suggests, macro viruses particularly target

macro language commands in applications like Microsoft
Word. The same is implied on other programs too.

Examples of

Viruses

Some of the known viruses are:

▪ Trojan horse virus

▪ Sleeper

▪ Logic bomb Alabama virus

▪ Christmas virus

▪ Jerusalem virus

▪ Resident virus

▪ Nonresident virus

▪ Code Red

▪ I love you

▪ Creeper virus

▪ Stone

▪ November 17

Sources of

Virus

These are the means through which viruses could be
spread from one system to the other.

▪ Infected memory devices

▪ E-mails attachments

▪ Internet downloads

▪ Computer network

▪ Illegal duplication of software/cracked software

▪ Unsecured websites

Virus

warning

signs

Some of the virus warning signs are listed below

▪ Slowing down response time

▪ Presence of tiny dots

▪ Wandering cursor across the screen

▪ Incomplete saving of files

▪ Corruption of the system set-up instruction

▪ The appearance of strange characters

▪ Insufficient memory space in a hard disk when you have

enough memory space

▪ Frequent system crash

▪ Unfamiliar applications or processes appearing on the

background

Virus

Detection
(Anti-Virus)

▪ Anti-viruses are also written programs by software

developers to stop and curb the spread of the virus in a
system.

▪ Antivirus software is a type of utility software used for

scanning and removing viruses from your computer. Once
an anti-virus is installed on a system, it will be hard for a
virus to enter the system except if the antivirus is
outdated.

▪ All antivirus can be updated on the internet.

Examples of

Antivirus
Programs

1.

Norton Anti-virus

2.

McAfee

3.

AVG

4.

Bitdefender

5.

Panda Dome

6.

Trend Micro

7.

Malwarebytes

8.

Avira Prime

9.

Intego

10.

TotalAV

11.

Bitdefender Total Security

12.

Dr Solomon’s Tool Kit

13.

Penicillin

14.

Avast

15.

Windows Defender

16.

Kaspersky

Benefits of
Antivirus to
Computer

▪ Protection from viruses

▪ Protection from spyware and identity theft

▪ Protection from spam

Computer

Virus

Preventive
Measures

Computer virus preventive measures include:
1. Install a good Computer Antivirus.
2. Timely update of the operating system.
3. Timely update of antivirus software
4. Installation of only trusted or licensed software
5. Exercise care when browsing the internet