The present invention provides a method, system, and computer program product for enhancing security within a distributed computing network while enabling fine-grained access control for packets traveling through the network. The disclosed techniques enable this fine-grained access control while simultaneously providing broad-brush application-independent and user-independent security for Internet Protocol (IP) packets that are in transit over both secure networks (such as a corporate intranet) and non-secure networks (such as the public Internet). Access control decisions are delegated to an access control engine, and are based upon mutually authenticated identity information (e.g. of a system user and/or application) that is extracted from information exchanged as part of an underlying security service (such as the Internet Key Exchange of the IP Security Protocol).