A virus is a small piece of software that inserts copies of itself into other executable programs and code in order to spread. It piggybacks on real programs to execute. There are several types of viruses including boot sector viruses, which infect the boot sector and slow down or stop system operations, and macro viruses, which are associated with applications like Word and Excel and destroy data when an infected document is opened. It is important to take actions like updating anti-virus software weekly, having backups, and being cautious of unexpected email attachments to prevent virus infections.

1. Virus
BOHAIR NASEER
13 BS ( IT )

2. A virus is a small piece of software that
piggybacks on real programs in order to get
executed
Once it’s running, it spreads by inserting
copies of itself into other executable code or
documents
Definition of Virus

3. Computer Virus Timeline
• 1949
Theories for self-replicating programs are first developed.
• 1981
Apple Viruses 1, 2, and 3 are some of the first viruses “in the wild,” or in the
public domain. Found on the Apple II operating system, the viruses spread
through Texas A&M via pirated computer games.
• 1983
Fred Cohen, while working on his dissertation, formally defines a computer
virus as “a computer program that can affect other computer programs by
modifying them in such a way as to include a (possibly evolved) copy of
itself.”
• 1986
Two programmers named Basit and Amjad replace the executable code in
the boot sector of a floppy disk with their own code designed to infect each
360kb floppy accessed on any drive. Infected floppies had “© Brain” for a
volume label.
• 1987
The Lehigh virus, one of the first file viruses, infects command.com files.
• 1988
One of the most common viruses, Jerusalem, is unleashed. Activated every
Friday the 13th, the virus affects both .exe and .com files and deletes any
programs run on that day.
MacMag and the Scores virus cause the first major Macintosh outbreaks.

4. Types of Computer Virus
Time Bomb
Logical Bomb
Worm
Boot Sector Virus
Macros Virus
Trojan Horse
Script Virus

5. Time Bomb
A time bomb is a virus program
that performs an activity on a
particular date

6. Logical Bomb
A logical bomb is a destructive
program that performs an activity
when a certain action has occurred.

7. Worm Virus
A worm is also a destructive
program that fills a computer
system with self-replicating
information, clogging the system so
that its operations are slowed
down or stopped

8. Boot Sector Virus
A boot sector virus infects boot
sector of computers. During system
boot, boot sector virus is loaded
into main memory and destroys
data stored in hard disk

9. Macro Virus
A macro virus is associated with
application software like word and
excel. When opening the infected
document, macro virus is loaded
into main memory and destroys the
data stored in hard disk

10. Script Virus
Commonly found script viruses are
written using the Visual Basic
Scripting edition (VBS) and the
JavaScript programming languages

11. Trojan Horse
Trojan Horse is a destructive
program. It usually pretends as
computer games or application
software. If executed, computer
system will be damaged.

12. Trojan Horse
Trojan Horse usually comes with
monitoring tools and key loggers

13. Actions to prevent virus infection
Always update your anti-virus
software at least weekly.
Back up your important files and
ensure that they can be restored.
Change the computer's boot
sequence to always start the PC
from its hard drive

14. Actions to prevent virus infection
Don't share Drive C: without a
password and without read-only
restrictions.
Empty floppy drives of diskettes
before turning on computers,
especially laptops.

15. Actions to prevent virus infection
Forget opening unexpected e-mail
attachments, even if they're from
friends
Get trained on your computer's
anti-virus software and use it.
Have multiple backups of
important files. This lowers the
chance that all are infected.

16. Actions to prevent virus infection
Install security updates for your
operating system and programs as
soon as possible.
Jump at the chance to learn more
about your computer. This will help
you spot viruses.

17. Reference
• http://mirror.aarnet.edu.au/pub/code-red/newframes-small-log.gif
• http://www.factmonster.com/ipka/A0872842.html
http://www.faqs.org/faqs/computer-virus/new-users/
• http://www.mines.edu/academic/computer/viri-sysadmin.htm