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UDP
Unknown
123 NTP
NTP keeps hosts synchronized to authoritative time sources so logs, certs, and scheduled jobs remain trustworthy.
Security Context
Port 123 is context-dependent. Its risk depends on the daemon behind it, whether the traffic is encrypted, and how tightly the listener is scoped to trusted networks.
- !Open NTP endpoints have historically been used for amplification attacks.
Nmap Check
Use a version probe first so you confirm whether the expected service is really what is listening on this port.
nmap -sU -p 123 <host>Firewall Commands
UFW
sudo ufw allow 123/udpiptables
sudo iptables -A INPUT -p udp --dport 123 -j ACCEPT