The Security Appliance supports application inspection through the Adaptive Security Algorithm function. Through the stateful application inspection used by the Adaptive Security Algorithm, the Security Appliance tracks each connection that traverses the firewall and ensures that they are valid. The firewall, through stateful inspection, also monitors the state of the connection to compile information to place in a state table. With the use of the state table in addition to administrator-defined rules, filtering decisions are based on context that is established by packets previously passed through the firewall. The implementation of application inspections consists of these actions:
http://www.cisco.com/en/US/products/ps6120/products_configuration_example09186a008081042c.shtml#configs3
