Which of the following would be considered a time source for synchronization?

• A. Network Time Protocol server
• B. Printed manual clock
• C. User login banner
• D. Email server

Answer: (A)

Time synchronization relies on a single, trusted reference clock that all devices in the environment use to set their own clocks, so event timestamps line up across systems. The Network Time Protocol server provides exactly that: a centralized time reference that devices can periodically query to adjust their internal clocks, often to UTC. This keeps logs from different machines comparable, which is essential for accurate auditing and incident response in PCI environments.

A printed manual clock can’t be used by systems to automatically synchronize, and it will drift over time. A user login banner contains text shown at login and has no role in providing time references. An email server, while it uses timestamps, isn’t a centralized time source that synchronizes other devices’ clocks.