Computer viruses are programs that infect computers without permission. The first virus, called Creeper, was created in 1971 and spread via ARPANET. Viruses can slow computers, cause crashes, and delete files. Common ways to get viruses include opening infected email attachments, visiting malicious websites, and downloading untrusted files. Antivirus software scans for and removes viruses, but must be kept up to date to defend against new threats. Over 6,000 new viruses are created each month, so vigilance is important to avoid infection.

2. Overview
Meaning
History
How do we get viruses ?
Effects of computer viruses
Types of computer infections
Keeping computer virus free
Anti-viruses
Some facts
Conclusion

3. Meaning
• A computer virus is a program or piece of code that is loaded onto
your computer without your knowledge and runs against your
wishes. Viruses can also replicate themselves. All computer viruses
are man-made. A simple virus that can make a copy of itself over
and over again is relatively easy to produce. Even such a simple
virus is dangerous because it will quickly use all available memory
and bring the system to a halt. An even more dangerous type of
virus is one capable of transmitting itself across networks and
bypassing security systems.

4. History…
• The Creeper virus was first detected on ARPANET, the forerunner
of the Internet, in the early 1970s.
• Creeper was an experimental self-replicating program written by
Bob Thomas at BBN Technologies in 1971.
• Creeper used the ARPANET to infect DEC PDP-10 computers
running the TENEX operating system.
• Creeper gained access via the ARPANET and copied itself to the
remote system where the message, "I'm the creeper, catch me if
you can!" was displayed. The Reaper program was created to
delete Creeper.

5. How Do We Get Viruses ?
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Sharing music, files or photos with other users
Visiting an infected Web site
Opening spam email or an email attachment
Downloading free games, toolbars, media players and other
system utilities
Installing mainstream software applications without fully
reading license agreements

6. Effects of Viruses
Slow computer performance
Erratic computer behavior
Unexplained data loss
Frequent computer crashes
Sapping computer memory
 Files/Directories disappear
 Denial of service

7. Types of Computer Infection
Viruses

8. Meaning….
Trojans
Viruses
Worms
Those on the receiving end
of a Trojan Horse are
usually tricked into opening
them because they appear
to be receiving legitimate
software or files from a
legitimate source.
Like a human virus, a
computer virus can range in
severity: some may cause
only mildly annoying effects
while others can damage
your hardware, software or
files
Worms spread from
computer to computer, but
unlike a virus, it has the
capability to travel without
any human action

9. Keeping Computer Virus Free
• Install anti-virus software from a reputable vendor. Update it and use it
regularly.
• In addition to scanning for viruses on a regular basis, install an "on
access" scanner (included in most anti-virus software packages) and
configure it to start each time you start up your computer. This will
protect your system by checking for viruses each time you run an
executable file.
• Use a virus scan before you open any new programs or files that may
contain executable code. This includes packaged software that you buy
from the store as well as any program you might download from the
Internet.

10. Keeping Computer Virus Free…
• If you are a member of an online community or chat room, be very
careful about accepting files or clicking links that you find or that
people send you within the community.
• Make sure you back up your data (documents, bookmark files,
important email messages, etc.) on disc so that in the event of a
virus infection, you do not lose valuable work.
• Scan all incoming email attachments
• The more computers flash cards, CDs, zip cards and floppies have
been used on, the better the chance of a virus infecting them –
clean them before use

11. Anti-viruses
• “Antivirus" is protective software designed to defend your
computer against malicious software. Malicious software, or
"malware" includes: viruses, Trojans, keyloggers, hijackers,
dialers, and other code that vandalizes or steals your computer
contents. In order to be an effective defense, your antivirus
software needs to run in the background at all times, and should
be kept updated so it recognizes new versions of malicious
software.

13. Some facts…
• Mydoom Virus in January 2004 infected almost 1 million computers
in as little as one day
• Melissa Virus in March 1999 was powerful enough to have Microsoft
and various other companies to shut down emailing systems until
the virus could finally be stopped.
• Storm Worm in January 2007 was said to have infected 50,000
computers by October of that year.
• Over 6,000 new computer viruses are released every month.

14. Some facts…
• The first virus that came into wild was elk cloner virus.This virus
was created by Richard Skrenta in 1981 when he was a student in
high school.He created it as a joke and inserted it in a game on a
floppy disk.The elk cloner virus get activated on its 50th use and
displays a poem "Elk Cloner: The program with a personality."
• Farooq Alvi Brothers of Lahore,Pakistan created the first pc virus
in 1986.It was a boot sector virus.
• The term virus to denote a self replicating program was first used
in 1969 in a short story of a Galaxy Magaine written by David
Gerrold.

15. Conclusion…
• I think with enough knowledge about viruses and the right kind of
software they can almost be preventable, you just have to use
common sense.
• Don’t open emails and download software that does not look like
it is from a reliable source
• Download Software that prevents and helps protect against
viruses