| ACLs are the first line of defense in a layered security approach. They permit authorized packets and deny unauthorized packets based on port or service type. They enhance the posture of the network by not allowing packets to even reach a potential target within the security domain. The PPS Vulnerability Assessment report contains a list of highly susceptible ports and services that should be blocked or limited as much as possible without adversely affecting customer requirements. Auditing packets attempting to penetrate the network, but that are stopped by an ACL, will allow network administrators to broaden their protective ring and more tightly define the scope of operation.
If the perimeter devices are in a deny-by-default posture and what is allowed through the filter is IAW DoD Instruction 8551.1, and if the permit rule is defined with explicit ports and protocols allowed, then all requirements related to PPS being blocked would be satisfied. It is the responsibility of the enclave owner to have the applications the enclave uses registered in the PPSM database. This requirement is usually implemented by the router, firewall, and/or the IDPS working jointly to ensure perimeter defense. |
