This document provides information about computer viruses and firewalls in 3 paragraphs. It first discusses various types of computer viruses like time bombs, logical bombs, worms, boot sector viruses, macro viruses, script viruses, and trojan horses. The second paragraph lists actions that can be taken to prevent virus infections, such as updating antivirus software weekly, backing up important files, and not opening unexpected email attachments. The third paragraph describes different types of firewalls - packet filtering firewalls, application gateways, and circuit level gateways - and provides brief details about how each works.

1. A Presentation of Network System
VIRUS and FIREWALLS
Submitted To: Submitted By:
Miss Malti Vikash MainanwaI
Department of Computer Science & Engineering
Punjab Institute of Technology, Kapurthala
(PTU Main Campus)

2. *CONTENTS*
•Virus
•Virus Types
•Action To prevent virus
•Firewalls
•Types of firewalls

4. Computer Virus

5. What is computer virus?
Computer virus refers to a
program which damages computer
systems and/or destroys or erases
data files

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

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

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

9. 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

10. 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

11. 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

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

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

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

15. 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

16. 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.

17. 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.

18. 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.

19. Firewalls
• Firewall is used to protect the network from
unauthorized access.
• A firewall is a junction of gateway between
the two network

20. Types of Firewalls
• Packet Filtering firewalls
• Application Gateway
• Circuit level Gateway

21. Packet filtering firewalls
• A Packet Filter Firewall apply set of rules
to each packet based on traffic it decide
either forward packet or discard
• Also called screening router firewall
• The rules are based on TCP/IP Header
• Source/Destination IP Address
• Source/Destination port number

23. Advantage of Packet Firewalls
• Low cost and low impact on network performance
• Mostly router support packet filtering feature
• This type of firewall works at network layer

24. Application level Gateway
• Is also called proxy server
• It acts like a proxy and decide about flow of
communication

25. Circuit level Gateway
• It works on Session layer and TCP layer
• This is useful for hiding the information
about the protecting network
• A circuit gateway creates a new connection
between itself and remote system

26. Circuit……

27. Any Query