Computer viruses are small programs that spread from computer to computer and interfere with operations. They are deliberately created by programmers for reasons like research, pranks, attacks, or financial gain. Viruses typically spread through email attachments, downloads, or infected files on removable drives. Symptoms of infection include slow performance, file changes or damage. People can protect computers by only opening trusted email attachments, backing up files, scanning downloads, and using antivirus software.

1. Presented by:
Maximino E. Santos Jr.
Computer Teacher-PNHS
COMPUTER VIRUS

2. What is a Computer Viruses
Computer Viruses are small software
programs that are designed to spread
from one computer to another and to
interfere with computer operation.

3. Why people create computer viruses
• Computer viruses do not come into existence
spontaneously. They are deliberately created by
programmers, or by people who use virus creation
software.
• Virus writers can have various reasons for creating and
spreading malware. Viruses have been written as
research projects, pranks, to attack the products of
specific companies, to distribute political messages, and
financial gain from identity theft, spyware, and
cryptoviral extortion. Some virus writers consider their
creations to be works of art, and see virus writing as a
creative hobby.

4. Ways of computer viruses enter your
computer
Viruses are most easily spread by attachments in e-mail
messages or instant messaging messages. That is
why it is essential that you never open e-mail
attachments unless you know who it's from and you
are expecting it. Viruses can be disguised as
attachments of funny images, greeting cards, or
audio and video files. Viruses also spread through
downloads on the Internet. They can be hidden in
illicit software or other files or programs you might
download.

5. How to detect virus?
Some Symptoms
•Program takes longer to load.
•The program size keeps changing.
•The drive light keeps flashing when you are
not doing anything.
•User created files have strange names.
•The computer doesn't remember CMOS
settings.

6. Examples of computer viruses
Trojan Horse:
A destructive program that masquerades as a
benign application. Unlike viruses, Trojan
horses do not replicate themselves but they
can be just as destructive. One of the most
insidious types of Trojan horse is a program
that claims to rid your computer of viruses but
instead introduces viruses onto your
computer.

7. Worm:
A worm is similar to a virus by its design, and
is considered to be a sub-class of a virus.
Worms spread from computer to computer,
but unlike a virus, it has the capability to
travel without any help from a person. A
worm takes advantage of file or information
transport features on your system, which
allows it to travel unaided. The biggest danger
with a worm is its capability to replicate itself
on your system, so rather than your computer
sending out a single worm, it could send out
hundreds or thousands of copies of itself,
creating a huge devastating effect.

8. Bootsector Virus :
A virus which attaches itself to the first part of the
hard disk that is read by the computer upon boot up.
These are normally spread by floppy disks.
Macro Virus:
Macro viruses are viruses that use another
application's macro programming language to
distribute themselves. They infect documents such
as MS Word or MS Excel and are typically spread to
other similar documents.
Memory Resident Viruses:
Memory Resident Viruses reside in a computers
volitale memory (RAM). They are initiated from a
virus which runs on the computer and they stay in
memory after it's initiating program closes.

9. Spy ware
• Spyware, on the other hand, is generally not
designed to damage your computer. Spyware is
broadly defined as any program that gets into
your computer without permission and hides in
the background while it makes unwanted
changes to your user experience.
• most spyware targets only the Windows
operating system. Some of the more notorious
spyware companies include Gator, Bonzi Buddy,
180 Solutions, DirectRevenue, Cydoor,
CoolWebSearch, Xupiter, XXXDial and
Euniverse.

10. How Did it Get on Your Computer?
• Spyware usually gets onto your machine
because of something you do, like clicking
a button on a pop-up window, installing a
software package or agreeing to add
functionality to your Web browser

11. How Did it Get on Your Computer?
• Drive-by download - This is when a Web site or
pop-up window automatically tries to download
and install spyware on your machine
• Browser add-ons - These are pieces of software
that add enhancements to your Web browser, like
a toolbar, animated pal or additional search box.
• browser hijackers -- these embed themselves
deeply in your machine and take quite a bit of
work to get rid of.

12. Steps to avoid virus
• Don’t open e-mail that you are not sure.
• All thumbdrive need to scan by anti-virus
software.
• Always scan your PC with anti-virus software.

13. How to protect your computer from
computer viruses
• Only open e-mail attachments received from
sources you trust and that you are expecting.
• Back up your hard drive files frequently and
maintain multiple backup sets.
• If you are experiencing unusually slow
performance, apparent file loss or damage, or
other abnormalities, immediately check your
hard drives and diskettes for infection.

14. •Delete chain emails and junk email. Do not
forward or reply to any to them. These types of
email are considered spam, which is
unsolicited, intrusive mail that clogs up the
network.
•Download software only from sites you are
familiar with, and immediately check it with
your anti-virus software.
•Don't spread hoaxes and rumors.

15. TOP 10 ANTIVIRUS OF 2010
1. BitDefender Antivirus
2. Kaspersky Anti-Virus
3. Webroot AntiVirus with SpySweeper
4. Norton AntiVirus
5. ESET Nod32 Antivirus
6. AVG Anti-Virus
7. F-Secure Anti-Virus
8. G DATA AntiVirus
9. Avira AntiVir
10.Trend Micro

16. End

17. References
• http://www.webopedia.com/DidYouKnow/Internet/2004/virus.asp
- The Difference Between a Virus, Worm, and Trojan Horse.
• http://en.wikipedia.org/wiki/Computer_virus - Computer
Virus
• http://www.microsoft.com/protect/computer/basics/virus.mspx
- What is Computer Viruses
• http://www.soe.umich.edu/computingnetwork/howto/avoidviruse
- How To Avoid Computer Viruses