Packet Filtering – a means of controlling access to aCisco IOS Access Control List (ACL) is one of the most used packet filters. IPChains is also a popular packet filter
Two-way communication presents a challenge for network security based on packet filtering. If one blocks all incoming traffic, one prevents responses to outgoing traffic from coming in, disrupting communication. Consequently, one has to open two holes, one for outgoing traffic and one for incoming traffic, without enforcing any association of the incoming traffic with existing outgoing connections in the network. Packet filtering thus can allow in crafted malicious packets that appear to be part of existing sessions, causing damage to protected resources.
Packet filtering devices do not track dynamic