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TCP
Vulnerable
139 NetBIOS Session Service
NetBIOS sessions carry Windows file and printer sharing traffic in legacy environments.
Security Context
Port 139 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.
- !Legacy SMB over NetBIOS should rarely be internet-accessible.
Nmap Check
Use a version probe first so you confirm whether the expected service is really what is listening on this port.
nmap -sV -p 139 <host>Firewall Commands
UFW
sudo ufw allow 139/tcpiptables
sudo iptables -A INPUT -p tcp --dport 139 -j ACCEPT