Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

1. Virus and Anti-Virus

2. BY: Adeel Rasheed
 Superior University

3. CONTENTS
• What is Virus?
• Types of Virus
• Types of Anti-Virus
• How does Anti-Virus Works
• Some Anti-Virus Software's which are available
in market

4. What is Computer Virus?
• Computer viruses are small software programs
that are designed to spread from one computer to
another and to interfere with computer operation.
• A virus might corrupt or delete data on your
computer, use your e-mail program to spread itself
to other computers, or even erase everything on
your hard disk.

5. Virus
Infection of more than 75,000 computers in 10 minutes

6. Source of Viruses
• Funny images
• Greeting cards
• Audio and video files
• E-mail messages
• Through downloads on the Internet
• CD,DVD,USB, Memory cards,etc

7. Types of Viruses
• Macro Viruses
• Memory Resident Viruses
• Overwrite Viruses
• Direct Action Viruses
• Directory Virus
• Web Scripting Virus
• Multipartite Virus
• FAT Viruses
• Companion Viruses
• Polymorphic Virus
• Email Virus

8. Macro Viruses:
These viruses infect the files created using some applications or
programs that contain macros such as doc, pps, xls and mdb.
Memory Resident Viruses:
They usually fix themselves inside the computer memory. They get
activated every time the OS runs and end up infecting other opened
files. They hide in RAM.
Overwrite Viruses:
These types of viruses delete any information in a file they infect,
leaving them partially or completely useless once they are infected.
Direct Action Viruses:
These viruses mainly replicate or take action once they are executed.
When a certain condition is met, the viruses will act by infecting the files
in the directory or the folder specified in the AUTOEXEC.BAT. The
viruses are generally found in the hard disk’s root directory, but they
keep on changing location.

9. Directory Virus:
Also known as cluster virus or file system virus. They infect the
computer’s directory by changing the path indicating file location.
They are usually located in the disk
Web Scripting Virus:
Most web pages include some complex codes in order to create an
interactive and interesting content. Such a code is often exploited to
cause certain undesirable actions.
Multipartite Virus:
These type of viruses spread in many different ways. Their actions
vary depending on the OS installed and presence of certain files. They
tend to hide in the computer’s memory
FAT Viruses:
These lardy viruses attack the file allocation table (FAT) which is the
disc part used to store every information about the available space,
location of files, unusable space etc.

10. Companion Viruses:
These types of viruses infect files just like the direct action and the
resident types. Once inside the computer
Polymorphic Viruses:
In a different way every time they infect your computer. They use
different encryption and algorithms.
This makes it difficult for the antivirus software to locate them using
signature or string searches
Email Virus:
This is a virus spread via an email. Such a virus will hide in an email
and when the recipient opens the mail.

11. What is Anti-Virus software?
Computer programs intended to Identify and
Eliminate Computer Viruses.

12.  Antivirus software is a class of program that searches a
hard drive and floppy disk for any known or potential
viruses.
 Also search from remove able disk.
 Anti-virus is a software that scans files or your
computer's memory for certain patterns that may indicate
an infection.

13. Types of Scans
• Automatic scans:
Depending what software you choose, you may be able to
configure it to automatically scan specific files or directories
and prompt you at set intervals to perform complete scans.
• Manual scans:
It is also a good idea to manually scan files you receive from
an outside source before opening them.

14. Main types of Anti-Virus
There are different types of antivirus software for
different computers
 Some are designed for personal computers.
 Some are for servers

15. How Antivirus software works?
Interception
Destination System
Source System
Alert
Disinfection

16. Anti-virus applications maintain a database of known
viruses and compare scanned files that match the
characteristics of known viruses. If a scanned files
matches those characteristics of known viruses. If a
scanned file matches those characteristics, it is
quarantined so that it cannot affect other files on
your system.
Once the file is quarantined, the application can
attempt to repair it, delete it, or prompt you for a
decision on what to do about the file infected

17. Best Antivirus software
available in market

18. Bit defender Antivirus
• This years best defense against computer viruses, spyware,
hackers and spam is an antivirus program called Bit Defender.
• Has a user-friendly interface that scans all existing files on your
computer, all incoming and outgoing emails, and even IM
transfers.
• Features include privacy protection and web scanning for
internet use. a years subscription is about $29.95

19. NAV
• The most widely used software is the Norton Antivirus. (NAV)
• Since its release in 1990, over 100 million people around the
world have used it.
• It’s a free program but in order to receive live updates, a valid
subscription is needed.
• A yearly subscription is only $49.99

20. McAfee
• McAfee Virus Scan is another popular antivirus program.
• It’s designed for home and home-office use.
• It’s used specifically on a Microsoft Windows platform.
• The includes a number of features including on access file
sharing, inbound and outbound firewall protection.
• A yearly subscription is only $59.99

21. Kaspersky
• For the average home user and advanced users the
Kaspersky antivirus software has an easy to use interface.
• The program uses 3 tabs for protection, settings and support.
• It updates itself on an hourly basis and is one of the fastest
antivirus programs available.
• However, quality comes at a price and year subscription is
$59.99.

22. Avast
• The boot-time scanner, Network Shield, and e-mail scanner in
Avast has attracted end-users.
• The detection capability of Alwil Avast! is very good and you can
install the program in any edition of Windows.
• The installer of Avast is bundled with Google Chrome browser
that is not necessary to continue using the antivirus program.
• A yearly subscription is only $34.99

23. Thanks