Packet Filter Firewall controls the network access by analyzing the outgoing and incoming packets. It lets a packet pass or block its way by comparing it with pre-established criteria like allowed IP addresses, packet type, port number, etc. Packet filtering technique is suitable for small networks but gets complex when implemented to larger networks. It is to be noted that these types of firewalls cannot prevent all types of attacks. They can neither tackle the attacks that use application layers vulnerabilities nor can fight against spoofing attacks.