The slide show is about the Firewall , why we need firewall , its advantages, disadvantage and is common types - packet-filter firewall and proxy firewall .its working and advantages and didadvantages.

1. FIREWALL

2. INTRODUCTION:
• Many organizations have confidential information, such as trade secrets,
product development plans, marketing strategies, etc., which should be
protected from access and modification.
• One possible approach is to use suitable encryption/decryption technique,
but it does not completely protect data from third party or hacker.
• So it is necessary to perform user authentication and access control to
protect the networks from unauthorized traffic. - Firewall.
• Firewall is used to protect a local system or network of systems from
network-based security threats.
• It protects and controls the interface between a private network and an
insecure public network.

3. Fig: Schematic diagram of a Firewall

4. Firewall Capabilities :
• It prevents vulnerable services from entering or leaving the network.
• It provides protection from various kinds of IP spoofing .
• It provides a location for monitoring security-related events .
• Audits and alarms can be implemented on the firewall systems.
Limitations of a Firewall :
• A firewall cannot protect against any attacks that bypass the firewall.
• A firewall does not protect against the internal threats from traitors.
• Firewall cannot protect against the transfer of virus-infected programs or
files.

5. TYPES OF FIREWALL
A firewall is usually classified as :
i. Packet-filter firewall
ii. Proxy-based firewall

6. PACKET-FILTER FIREWALL

7. • A firewall may act as a packet filter.
• It can operate as a
Positive filter: Allowing to pass only packets that meet specific criteria
Negative filter: Rejecting any packet that meets certain criteria.
• A packet filtering firewall applies a set of rules to each incoming and
outgoing IP packet and then forwards or discards the packet.
• Filtering rules are based on information contained in a network packet:
1. Source IP address: The IP address of the system that originated the
packet.
2. Destination IP address: The IP address of the system the IP packet is
trying to reach.
3. Source and destination transport-level address: The transport-level
(e.g., TCP or UDP) port number, which defines applications such as
SNMP or TELNET

8. 4. IP protocol field: Defines the transport protocol.
5. Interface: For a firewall with three or more ports, which interface of the
firewall the packet came from or which interface of the
firewall the packet is destined for.
If packet filtering rules are satisfied, a packet can be transferred
through a wall. If not it will be removed.

9. Advantages:
• Simplicity.
• Transparency to users.
• High speed.
Disadvantages:
• Difficulty of setting up filter rules.
• Lack of authentications (IP spoofing.)

10. APPLICATION-LEVEL GATEWAY
• Also known as application proxy or application-level proxy.
• It is an application program that runs on a firewall system(between two
networks).
• It is designed to protect against outside attackers.

11. • The user contacts the gateway using a TCP/IP application(Telnet or FTP)
and the gateway asks the user for the name of the remote host to be
accessed.
• When the user responds and provides a valid user ID and authentication
information, the gateway contacts the application on the remote host and
relays TCP segments containing the application data between the two
endpoints.
• This creates two connections: one between the client and the proxy server
and one between the proxy server and the destination.
• Once connected, the proxy makes all packets forwarding decision.
• since all communication is conducted through the proxy server, computers
behind the firewall is protected.

12. Advantages:
• Higher security than packet filters.
• Only need to verify only few allowable applications.
• Easy to log and audit.
Disadvantages:
• Additional processing overhead on each connection.