Port 139 is utilized by NetBIOS Session service. Enabling NetBIOS services provide access to shared resources like files and printers not only to your network computers but also to anyone across the internet.

Is port 139 still needed?

If you are on Windows-based network that is running NetBios, it is perfectly normal to have port 139 open in order to facilitate that protocol. If you are not on a network using NetBios, there is no reason to have that port open.

What are ports 137 and 139 used for?

Port 135 is used for RPC client-server communication, and ports 139 and 445 are used for authentication and file sharing. UDP ports 137 and 138 are used for local NetBIOS browser, naming, and lookup functions.

Is it safe to have port 139 open?

Firewalls, as a measure of safety always block this port first, if you have it opened. Port 139 is used for File and Printer Sharing but happens to be the single most dangerous Port on the Internet. This is so because it leaves the hard disk of a user exposed to hackers.

Why is NetBIOS still used?

NetBIOS (Network Basic Input/Output System) was created in the early 1980's, but is surprisingly still alive and well on many networks today. Microsoft Windows still uses it for its name resolution function (often by default), when DNS is not available.

What is an SMB Port? What is Port 445 and Port 139 used for?

Should I block port 139?

Port 139 is utilized by NetBIOS Session service. Enabling NetBIOS services provide access to shared resources like files and printers not only to your network computers but also to anyone across the internet. Therefore it is advisable to block port 139 in the Firewall.

How do I close 139?

To close port 139 (netbios-nbsession):

1. Click on "Start" → "Settings" → "Control Panel"
2. Double click on "Network"
3. Select the "Configuration" tab.
4. Scroll down network component list and find and select item starting with "TCP/IP -> ..."
5. Then select "Properties"
6. Select the "Bindings" tab.
7. Deselect each option then click "Ok"

How do I open port 139 on Windows?

Open firewall ports in Windows 10

1. Navigate to Control Panel, System and Security and Windows Firewall.
2. Select Advanced settings and highlight Inbound Rules in the left pane.
3. Right click Inbound Rules and select New Rule.
4. Add the port you need to open and click Next.

What are ports 139 and 445 used for?

Port 139 is used by SMB dialects that communicate over NetBIOS. It's a transport layer protocol designed to use in Windows operating systems over a network. Port 445 is used by newer versions of SMB (after Windows 2000) on top of a TCP stack, allowing SMB to communicate over the Internet.

What port does DHCP use?

DHCP is a network protocol to used to configure IP networks. A DHCP server listens to UDP port 67 and dynamically assigns IP addresses and other network parameters to DHCP clients. These clients will listen for responses on UDP port 68.

What port does SSH use?

By default, the SSH server still runs in port 22.

What port does NetBIOS use?

More information. NetBIOS over TCP traditionally uses the following ports: NBName: 137/UDP. NBName: 137/TCP.

Which port is used for telnet?

The default port for Telnet client connections is 23; to change this default, enter a port number between 1024 and 32,767.

What is NetBIOS server?

NetBIOS (Network Basic Input/Output System) is a network service that enables applications on different computers to communicate with each other across a local area network (LAN). It was developed in the 1980s for use on early, IBM-developed PC networks.

How do I open port 139 on Windows server 2012?

Click on Windows Firewall With Advanced Security. At Windows Firewall With Advanced Security, click on Inbound Rules >> New Rule. At New Inbound Rule Wizard, Select Port Radio button and click Next. Select TCP/UDP & specify the port you wish to open in Specific Local Ports box OR check All local ports & click Next.

How do I check which ports are open on my router?

Type "netstat -a" at the command prompt and press "Enter." After a few seconds, all of the open ports on the computer. Locate all of the entries that have an "ESTABLISHED," "CLOSE WAIT" or "TIME WAIT" value under the "State" header. These ports are also open on the router.

Is NetBIOS a security risk?

Vulnerabilities in Windows Host NetBIOS to Information Retrieval is a Low risk vulnerability that is also high frequency and high visibility. This is the most severe combination of security factors that exists and it is extremely important to find it on your network and fix it as soon as possible.

What is SMB used for?

The Server Message Block protocol (SMB protocol) is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network. It can also carry transaction protocols for interprocess communication.

Do I need NetBIOS enabled?

NetBIOS is legacy and you only need it if you are using old applications or old versions of Windows that require it or use WINS. If your running applications or OS's that require it still, NetBIOS is probably not the real problem here.

What happens if I disable NetBIOS?

As described earlier, NetBIOS uses the NBT protocol. NBT is vulnerable to poisoning attacks because it is not an authenticated protocol. A skilled hacker can impersonate or spoof the identity of NBT frames and misdirect traffic on the network, allowing sensitive information to be stolen.

What happens if I disable NetBIOS over TCP IP?

To improve performance, it's recommended that you disable NetBIOS over TCP/IP on your cluster network NIC and other dedicated-purpose NICs, such as for iSCSI and Live Migration. NetBIOS isn't used in Server 2008 R2 clusters. To disable NetBIOS over TCP/IP, access the IPv4 properties of your network adapter.