Computer Viruses have become a daily nuisance and we have to tackle it almost daily. Let's see what it is actually , who designs it and what are the methods by which we can tackle it.

1. By-
Anubhav Sinha
IX A

2. What’s Inside?
• What is a virus?
• More about virus
• Who wrote it and why?
• How do they spread?
• Kinds of virus……………….
• What is a worm?
• Difference between virus and worms
• 2014

3. What is a virus?
– An executable code
– That could make copies of itself or attach
itself to other executable codes
– Most of computer viruses have their
latency period.
– Attack programs or data on your hard
drive on a specific day when conditions
has been fulfilled.

4. More about Virus…..
• A virus is a small piece of software that piggybacks
on real programs.
• Computer viruses are called viruses because they
share some of the same traits of biological viruses.

5. Who write virus and why?
To prove their own theories.
– To see if they can do it.
– People who are political, religionary ardor.
– People usually publish their virus source
codes in BBSes or the Internet for users
who are interested in computer virus
programming.
– Most of them belong to specific
organizations

6. Difference between a worm and a virus
• Virus
– Usually small size programs ( 3-30k )
– Designed to evade detection
• Worm
– Sends itself to other systems
– Bigger in size than virus
– Not easy to write

7. From where does these virus spread?
• Medium
– Hard disk , Floppy disks , Tape
– Optical media
– Memory
• Internet
– E-mail attachments
– .exe .bat .vbs
• Research : One in every five hundred e-mail
messages contain a virus.

8. Kinds of virus

10. Memory Resident Virus
Hideout: This type of virus hides in the RAM
and stays there even after the malicious
code is executed
• Target: It can corrupt files and programs
that are opened, closed, copied, renamed,
etc.
• Examples: Randex, CMJ, Meve, and
MrKlunky
• Protection: Install an antivirus program.

11. Direct Action Viruses
Hideout: The viruses keep changing their
location into new files whenever the code
is executed, but are generally found in the
hard disk's root directory.
• Target: It can corrupt files.
• Examples: Vienna virus
• Protection: Install an antivirus scanner.

12. Overwrite Viruses
Hideout: The virus replaces the file content.
However, it does not change the file size.
• Examples: Way, Trj.Reboot, Trivial.88.D
• Protection: The only way to clean a file
infected by an overwrite virus is to delete
the file completely, thus losing the original
content.

13. Boot Sector Virus
• HIdeout: It hides in the memory until DOS
accesses the floppy disk, and whichever
boot data is accessed, the virus infects it.
• Examples: Polyboot.B, AntiEXE
• Protection: Ensure that floppy disks are
write-protected

14. Macro Virus
Hideout: These hide in documents that
are shared via e-mail or networks.
Examples: Relax, Melissa. A, Bablas,
O97M/Y2
Protection: Avoid opening e-mails from
unknown senders. Also, disabling macros
can help to protect your useful data.

15. Polymorphic Virus
Polymorphic viruses encrypt or encode
themselves in a different way (using
different algorithms and encryption keys)
every time they infect a system.
Examples: Elkern, Marburg, Satan Bug
and Tureen.
Protection: Install a high-end antivirus as
the normal ones are incapable of detecting
this type of virus.

16. FAT Virus
Hideout FAT virus attacks the FAT section and
may damage crucial information. It can be
especially dangerous as it prevents access to
certain sections of the disk where important files
are stored.
Examples: Link Virus
Protection: Before the virus attacks all the
files on the computer, locate all the files
that are actually needed on the hard drive,
and then delete the ones that are not
needed.

17. Multipartite Virus
Hideout: In the initial phase, these viruses
tend to hide in the memory as the resident
viruses do; then they infect the hard disk.
Examples: Invader, Flip and Tequila
Protection: You need to clean the boot
sector and also the disk to get rid of the
virus, and then reload all the data in it.

18. Trojans
• Trojans
In fact, it is a program which disguises
itself as a useful program or application.
▶ Beware of the fact that these viruses
copy files in your computer (when their
carrier program is executed) that can
damage your data, and even delete it.

19. 2014's Worst Viruses
! Flame: It is said to be the first of its kind that uses
Bluetooth as the spread medium. It was first detected in a
Russian lab.
! Belgian Computer Crime Virus: This virus spread
globally and asked the users for some vital information
and a processing fee, claiming that it was for police records.
! Shamoon: This virus is dangerous as it creates files of
the data on your hard disk, and then this compiled data is
sent to the attacker.