Viruses are programs that can copy themselves and infect computers without permission. They spread by downloading infected files from the internet or receiving emails with attachments containing viruses. Viruses avoid detection through encryption that hides their identity. Examples of viruses include Trojan horses, which harm computers quietly by installing malware alongside downloaded programs, and Salami attacks, which steal small amounts of money from accounts repeatedly without notice. To prevent viruses, users should have updated antivirus software and scan their computer weekly.

1. VIRUS
~ Presenters ~
Vincent Chong
Kwan Tak Wai
Chu Kean Chern

2. What is Virus
• A computer virus is a program
that can copy itself and infect the
computer without the permission
of the owner .

3. How viruses spread
Viruses can be spread by :
~ Downloading a file which contains
virus from the internet.
~ Receiving an email attachment that
includes virus.
~ Opening a given website link from
someone which is a virus website.

4. How virus avoids being detected
Viruses can prevents being detected in many ways ,
the following is the main prevention method :
~ Encryption . Viruses use encryption to hide their
identity . For example , you type the words “ABC” ,
then you encrypt the words you just typed , and
then the words “ABC” will become fake words like
“DEF”. (Also known as encrypted words)

5. Examples of Virus
• Trojan Horse
• Salami Attack
These are 2 examples :

6. What is Trojan Horse
• A trojan horse is a program that will do
harm to the computer quietly.
Example :
You download a free online game and install it.
When you are installing the game , the trojan
also will be installed without your awareness.
You play the game everyday , in the same time ,
the trojan will silently record the keys you have
pressed while typing your password and send it
to the creator of the trojan.

7. What is Salami Attack
• Salami attack is a program that steals commission
from someone without being noticed.
Example :
A bank worker insert a pen drive into a computer
that controls all the account of every customer ,
then the pen drive starts to transfer a small
amount of money from every customer’s account
to the bank worker’s own account without the
customer’s awareness.

8. Conclusion
• Have at least one antivirus on your
computer.
• Always keep your antivirus
updated.
• Scan your computer through
antivirus at least once a week.

9. References
• http://computer.howstuffworks.com/virus.htm
• http://www.scribd.com/doc/13503439/VirusTro
jan-HorseSalami-Attack