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UDP
Vulnerable
138 NetBIOS Datagram
NetBIOS datagrams support legacy browsing and messaging behavior on older Windows networks.
Security Context
Port 138 is high-risk when broadly exposed. Treat it as an attack-surface decision, not just a connectivity setting, and confirm whether the listener truly needs to be reachable.
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 138 <host>Firewall Commands
UFW
sudo ufw allow 138/udpiptables
sudo iptables -A INPUT -p udp --dport 138 -j ACCEPT