Firewall is a bridge between a computer and the network. It objective is to monitor the network traffic by viewing each incoming and outgoing packet. Firewall checks whether the packet should be allowed or not. It protects the PC from the Trojan horse attacks and other viruses. There are various research going on the implementation of the firewalls and the various security issues concerned with it. Next generation firewall deep inspection policy by integrating intrusion prevention system. Also Purdue university is developing a prototype firewall to prevent hacking of the medical devices.