Sure, here are some guidelines for NTP hardening based on available sources:
- Use NTP authentication and checking: NTP provides cryptographic security mechanisms such as message authentication to provide trusted time distribution. Implementing NTP authentication and checking mechanisms can prevent attackers from injecting false timestamps and other NTP attacks. [1][2]
- Minimize the number of network interfaces: Reducing the number of network interfaces that run NTP can limit exposure to NTP network-based attacks. [1]
- Use access control lists (ACLs) on NTP peers; Only allow traffic from trusted sources: Employ access control lists to restrict access to authorized devices and services only. Limiting traffic to trusted sources can prevent unauthorized access to the NTP services running on a device. [1]
- Disable NTP services on devices where not needed: If NTP synchronization is not needed on a machine, it is recommended to disable the service. Disabling NTP on a device reduces the attack surface of the device. [2]
- Use the latest stable version of the NTP software: Using updated software with the latest security patches helps reduce the attack surface by addressing known security vulnerabilities in the software. [2]
- Monitor the NTP traffic on the network: NTP traffic can be used in distributed denial-of-service (DDoS) attacks or timing-based covert channels. Monitoring the network traffic for abnormal NTP traffic can help detect such threats. [2]
Note that these are just general guidelines for NTP hardening, and organizations are advised to customize their approach based on their specific security requirements and environment.