COMPUTER VIRUS JS3 NOTES

 

COMPUTER VIRUS

MEANING, TYPES, EXAMPLES AND SOURCES OF VIRUS

Objectives: At the end of the lesson, students should be able to

i. Define computer virus

ii. List and explain types of viruses

Iii. List examples and sources of viruses     

 

Meaning of Computer Virus

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.

 

Types of Computer Viruses

1.    Boot Sector Virus- This type of virus infects the master boot record i.e removable media.

2.   Direct Action Virus- This is also called non-resident virus, when executed scans the disks for targets

3.   Resident Virus - Resident virus installs itself as part of the operating system when executed, after which it remain in the RAM from the time the computer is booted up to when it is shut down.

4.   Multipartite Virus- This type of virus spreads through multiple ways. It infects both the boot sector and executable files at the same time.

5.   Polymorphic Virus:-These types of viruses are difficult to identify with a traditional antivirus program. This is because the polymorphic viruses alter its signature pattern whenever it replicates.

6.   Overwrite Virus:-This type of virus deletes all the files that it infects. Identifying the overwrite virus is difficult as it spreads through emails.

7.    Space filler Virus- This is called so as they fill up the empty spaces between the codes and hence does not cause any damage to the file

8.    Macro viruses:-This 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:

a. Trojan horse virus

b. Sleeper

c. Logic bomb Alabama virus

d. Christmas virus

e. Jerusalem virus

f. Resident virus

g. Nonresident virus

h. Code Red

i. I love you

j. Creeper virus    k. Stone       l. November 17

 

Sources of Virus

 

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

i. Infected memory devices

ii. E-mails attachments

iii. Internet downloads

iv. Computer network

v. Illegal duplication of software/cracked software

VIRUS WARNING SIGNS
Some of the virus warning signs are listed below
i. Slowing down of response time
ii. Presence of tiny dots
iii. Wandering cursor across the screen
iv. Incomplete saving of file
v. Corruption of the system set-up instruction
vi. Appearance of strange characters
vii.Insufficient memory space in a hard disk when you have enough memory space

Virus Detection (Anti-Virus)
Anti-viruses are also written programs by software developers to stop and curb the spread of 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 are:
a. Norton Anti-virus
b. McAfee
c. AVG
d. Dr. Solomon’s Tool Kit
e. Penicillin
f. Avast
g. Windows defender
Other Virus preventive measures include:
1. Timely update of operating system.
2. Timely update of antivirus software
3. Installation of only trusted or licensed software
4. Exercise care when browsing the internet

Assignment

1.   Define computer virus

2.   List and explain any three (3) types of virus

3.   List five (5) examples of virus

4.   State four (4) sources of virus

5. State four (4) virus warning signs

6.  Define an Antivirus Program and list five (5) examples of antivirus software

7.  State three (3) Virus preventive measures