Guards, which often leverage MLS technologies themselves, filter traffic flowing between networks; unlike a commercial Internet firewall, however, a guard is built to much more stringent assurance requirements and its filtering is carefully designed to try to prevent any improper leakage of classified information between LANs operating at different security levels.
Sentinels, which often utilize MLS technologies themselves, screen traffic flowing between networks; unlike a commercial Internet firewall, however, a sentinel is constructed with more stringent assurance requirements and its filtering is meticulously designed to try to prevent any improper leakage of classified information between LANs operating at different security levels.