← Port Encyclopedia
139
NetBIOS-SSN
TCP
Windows
Critical Risk
NetBIOS Session Service — file sharing, printer sharing, EternalBlue (MS17-010)
🔍 How to Scan Port 139
nmap -sV -p 139 target
nmap -sV -sC --script=banner -p 139 target
nc -zv target 139
🛡️ Security Considerations
- Scan port 139 with
nmap -sVto identify the exact service and version - If NetBIOS-SSN is not needed, close or firewall this port immediately
- Check for default credentials if a management interface runs on this port
- Use
searchsploit netbios-ssnto find known exploits - Monitor traffic on port 139 with Wireshark or tcpdump for anomalies
- Ensure the service is patched to the latest version to prevent known CVE exploitation