Firewall

• A Firewall is a network security system,either hardware or software based, that monitors and controls incoming and outgoing network traffic based on predetermined security rules.
• Firewall applies security rules on each packet, this rules decide if a packet can pass, or whether it discarded.
• Usually firewall is palced between a network that is trusted, and one that is less trusted.





• A Firewall protects a number of computers on a LAN against unauthorised access.

Hardware Firewall :

• It is just a software firewall running on a specialized device.
• It is a hardware device that filters the information coming through the internet connection into your private network or computer system.
• It protects from Remote logins, Application backdoors, SMTP session hijacking,Email addresses,Spam.





• Firewall use one or three methods to control traffic flowing in and out of the network.
• Packet filtering : Packets are analyzed against a set of filters.
• Proxy service :Information from the internet is retrieved by the firewall and then sent to the requesting system and viceversa.
• State-full inspection :It compares certain key parts of the packet to a database of trusted information.information travelled from inside to the outside is monitored for specific defining characteristics then incoming information is compared to these characteristics.

Software Firewall :

• It is also called as Application level Firewall or Personal Firewall.
• It operating between the Datalink Layer and Network Layer. They filter packets at the Network Layer.





• It monitor the communication type(TCP,UDP,ICMP,etc) as well as the origination of the packet,and application(program)the packet is coming from or headed to.
• Requires manual configuration of each client computer.