FIREWALL

Firewall is used to help keep a network secure. Firewalls protect against hackers and malicious intruders. Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not.

Working:
A firewall examines all the traffic routed between the two networks (internal network and external network) to see if it meets certain criteria.
It routes packet between the networks. And most router support packet filtering.
It filters both inbound and outbound traffic.
Firewall can filter packet based on their source and destination addresses and port number.

Firewalls fall into four categories:

• Packet filters:- it work at the network level of the OSI model (or the IP layer of TCP/IP).  Each packet is compared to a set of criteria before it is forwarded.

• Circuit level gateway:- It work at the session layer of the OSI model, or the TCP layer of TCP/IP. They hide information about the private network they protect. It do not filter individual packet.

• Application level gateway:- It also called proxies, they can filter packet at the application layer of the OSI model. Incoming or outgoing packet cannot access service for which there is no proxy. They can filter an application specific command such as “http: post and get”.

• Stateful multilayer inspection firewall:- It combine the aspects of the other three types of firewall. They are expensive and require competent personnel to administer the device.

Types of Firewall:

1.      Software Firewall: Software firewall is inbuilt in windows.

 

There are three types of software firewall:-

• Zone Alarm

• Kspersky Internet Security 2011

• Comodo Internet Security 2011

2. Hardware Firewall: Hardware firewall is looks like DVD. It needs to be attached with you network.

 

         There are three types of hardware firewall:-

• Nebero

• Cyberom

• Juniper