A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. There are different types of firewalls including packet filters, application gateways, circuit-level gateways, and bastion hosts. A firewall inspects each packet of data and determines whether to allow it to pass through or block it from passing. Firewalls are used to prevent unauthorized access to private networks from the internet and can protect both individual computers and entire networks.

1. FIREWALL

2. Contents What is FireWall ? - Software vs. Hardware Firewall How does FireWall works ? Types of FireWall Techniques – > Packet filter > Application gateway > Circuit level gateway > Bastion host Conclusion: - What FireWalls can do ? - What FireWalls cannot do ?

3. What is FireWall ? FireWall is device that provides secure connectivity between networks (internal/external). A firewall may be a hardware , software , or a combination of both that is used to prevent unauthorized programs or Internet users from accessing a private network and/or a single computer.

4. Software vs. Hardware Firewalls Software Firewall Hardware Firewall -Protect a single computer -Usually less expensive, easier to configure -Protect an entire network. -Usually more expensive, harder to configure Norton Internet Security Cisco PIX Mcafee Internet Security NetScreen Outpost WatchGuard Ms. ISA Server Check Point

5. How does a Firewall work? Inbound to or outbound from your computer. Inspects each “ packet ” of data that arrives at either side of the firewall. Determines whether it should be allowed to pass through or if it should be blocked . sent sent received received packets packets

6. How a firewall works ? Sniffing Mode An attacker tries to compromise a service on the protected network. 2) The Firewall identifies the attempt . The FIREWALL can now: Alert the admin Harden the firewall Or reset a TCP/IP connection LOG Alert Reset Fire Wall 

7. Types of FireWall Techniques Packet filter Application gateway (a.k.a. Proxy server) Circuit-level gateway Bastion Host

8. Packet filter - It looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules . Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing . Packet Filtering Applications Presentations Sessions Transport DataLink Physical DataLink Physical Router Applications Presentations Sessions Transport DataLink Physical Network Network

9. Application gateway Application gateway (Proxy Server)- User uses TCP/IP applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. Applications Presentations Sessions Transport DataLink Physical Network DataLink Physical Applications Presentations Sessions Transport DataLink Physical Application Gateway Applications Presentations Sessions Transport Network Network Telnet HTTP FTP

10. Circuit-level gateway Circuit-level gateway- It is a stand alone application. It does not permit end-to-end TCP connection. It sets up 2 TCP connections: > B/w itself and a TCP user on an inner host. > B/w itself and a TCP user on an outer host.

11. Bastion host > Bastion host is a special purpose computer on a network specifically designed and configured to withstand attacks . > It generally hosts a single application , provides platform for Application gateway and Circuit-level gateway. It supports limited/specific applications to reduce the threat to the computer. Include applications- Telnet,SMTP,FTP.

12. Conclusion What a firewall can do ? What a firewall cannot do ?

13. What a personal firewall can do ? Stop hackers from accessing your computer. Protects your personal information . Blocks “ pop up ” ads and certain cookies . Determines which programs can access the Internet. Block invalid packets .

14. What a personal firewall cannot do ? Cannot prevent e-mail viruses Only an antivirus product with updated definitions can prevent e-mail viruses. After setting it initially, you cannot forget about it The firewall will require periodic updates to the rulesets and the software itself. Virus can jump Firewall !! F I R E W A L L Deadly Virus

15. SECURED Firewall Thank You…… Source – >CNS Text Book (William Stallings) > Wikipedia