Network Time Protocol Hardening

Network Time Protocol hardening is the set of controls that secure NTP, the protocol that synchronizes clocks across shipboard IT and OT networks. Accurate time matters because log correlation in a SIEM, certificate validity checks, and event sequencing all depend on it; a spoofed time source can mask an intrusion or invalidate X.509 certificates. Hardening uses authenticated NTP (symmetric keys or NTS, RFC 8915), restricted server lists, rate limiting, and a trusted internal stratum, reducing exposure to amplification and time-shifting attacks.