Port 139 NetBIOS
NetBIOS Session (TCP/IP), Windows File and Printer Sharing
Port 139 NetBIOS is the single most dangerous port on the Internet. All “File and Printer Sharing” on a Windows machine runs through this port. About 10% of all users on the Internet leave their hard disks exposed on this port. This is the first port hackers want to connect to, and the port that firewalls block.
If you use windows then you’ll probably have Port 139 NetBIOS open by default. Hackers can get to you, so unless you need “sharing”… you’re best to close the port.
Here’s how to disable NETBIOS over TCP/IP (close Port 139 NetBIOS)
Start → Control Panel (Category View) → ‘Network and Internet Connections’ → ‘Network Connections’.
Under ‘LAN or High Speed Internet’ of the ‘Network Connections Window’ — click once and highlight an item associated with your network card. Right click on that item and select ‘Properties’.
Under ‘Local Area Connection Properties’ — uncheck ‘Client for Microft Networks’ and ‘File and Printer Sharing for Microsoft Networks’.
(If you intend to use either of these with NetBEUI or IPX, then leave them checked).
Under the ‘General’ tab of the ‘Local Area Connection Properties’ window — click one on Internet Protocol (TCP/IP).
Under the ‘General’ tab of the ‘Internet Protocol (TCP/IP) Settings’ window — click on ‘Advanced’. In the ‘Advanced TCP/IP Settings’ window — click on ‘WINS’. Select Disable ‘NetBIOS over TCP/IP’.
Remove the check next to ‘Enable LMHOSTS lookup’.
Click OK on the Advanced TCP/IP setting window → click OK in the ‘Internet Protocol (TCP/IP) Settings’ window.
Click Close on the Local Area Connection Properties window → click Close the ‘Network Connections’ window using the ‘X’ button in the upper right corner or File → Close.
Finally, reboot your system.
Here’s a quick video tutorial of the process to disable Port 139 NetBIOS
