Which statement about different types of firewalls is not true?

The statement about stateful inspection firewalls mentions that they monitor all packets of a session, which is true. Stateful inspection firewalls keep track of the state of active connections and make decisions based on the context of the communication, which includes maintaining a state table where they store information about ongoing sessions. This allows them to recognize valid packets belonging to established connections or to identify packets that belong to new connections and ensure they are legitimate.

The other options provide accurate descriptions of different firewall types. Packet filtering firewalls indeed check each data packet against Access Control List (ACL) rules, allowing or denying packets based on predetermined criteria. Stateful inspection firewalls do require configuration for security policies in both directions because they manage bi-directional traffic and need to maintain state awareness of the connections. Proxy firewalls operate by acting as intermediaries for requests from clients seeking resources from other servers, effectively processing and filtering traffic between internal and external networks.

Therefore, the statement about stateful inspection firewalls does not contain any inaccuracies; thus, it is clear that the answer provided lacks the appropriate assessment.