NTP and SNTP packets are unauthenticated, making them vulnerable to spoofing attacks that can manipulate a device's system clock. The post explains how forged NTP packets can be sent or intercepted via ARP spoofing to alter system time on Linux (systemd-timesyncd), Windows, and Android. Linux's timesyncd is particularly vulnerable, accepting any time offset. Consequences of time manipulation include disrupted timed events, shifted access windows, broken cryptographic guarantees (TOTP, TLS certificates, keystream replay), and corrupted distributed system data. The post recommends Network Time Security (NTS) as the proper mitigation, which adds authenticated key exchange to NTP, though adoption is still limited.
Table of contents
What is NTP?Sending forged NTP packetsIntercepting NTP packetsConsequences of NTP spoofingHow to prevent these attacks?2 Impressions