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INTRODUCTION Firewall is a concept which blocks unwanted traffic and passes desirable traffic to and from both sides of the network.

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Presentation on theme: "INTRODUCTION Firewall is a concept which blocks unwanted traffic and passes desirable traffic to and from both sides of the network."— Presentation transcript:

1 INTRODUCTION Firewall is a concept which blocks unwanted traffic and passes desirable traffic to and from both sides of the network

2 DEFINITION “A firewall is a system (either software or hardware or both) that enforces an access control policy between two networks” Intranet Firewalls -Scott Fuller & Kevin Pagan Example Allows : http, mails etc Keeps out: Intruders, Denial of services attacks, spam etc

3 OPERATION OF FIREWALL http://rr.sans.org/firewall/taxonomy.php courtesy:

4 Types of Firewalls Data is transferred in packets How a firewall works depends on how it determines which packet to allow and which to not This is dependent on the layer on which it operates Based on this there are three types Packet filtering (Network layer) Circuit level (Transport Layer) Application level (Application level)

5 PACKET FILTERING This is the most basic form Whenever the network receives a packet, three actions are possible Forward it to the destination Block it Return it to the sender One of these are chosen according to a “set of rules usually in a form of access control lists”

6 PACKET FILTERING Some of the factors which determines the actions are, Source address Destination address Direction of traffic etc Rules are applied top to bottom Ordered from least restrictive to most restrictive

7 IMPROVEMENTS Dynamic : Open and close apertures in the wall based on the information in the header Port Level Network Address translator : Secure internal servers Applets and CGI scripts

8 CIRCUIT LEVEL FIREWALLS Validates the sessions before opening connections (handshakes) Once a connection is made, all packets related to that connection are passed Packets are not scrutinized No direct connections Establishes two connections-between client, firewall and firewall, server

9 CIRCUIT LEVEL FIREWALLS Implemented by SOCKS Manipulating the established connection is easy

10 APPLICATION LEVEL FIREWALLS Also called Proxy server firewalls Basic operation Accept/Deny Rules Application Level Proxy Network Layer Outgoing PacketIncoming packet Application Level Network Level

11 APPLICATION LEVEL FIREWALLS Runs a proxy server application Two connections per session Proxy server evaluates the requests and decides according to the security concerns All packets are scrutinized Auditing is possible Adaptive proxy is more faster

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