Saying Goodbye to NetBIOS - 10-D Security
NetBIOS scan uses UDP port 137 to send and receive the NetBIOS data. If this port is blocked by your computer or in the remote network computers that you scan, the NetBIOS scan will not work. When you run NetBScanner in the first time, you might get a warning from the Firewall of Windows. The dangers of open port 139 - SearchSecurity I recently discovered I have an open port: 139. I did some research and found out it is a Netbios-ssn port used for sharing files. I have scanned for relevant Trojans and found none. nbtstat | Microsoft Docs
What is NetBIOS? Characteristics of NetBIOS - Stemjar
SMB ports are generally port numbers 139 and 445. Port 139: Used by SMB dialects that communicate over NetBIOS, a transport layer protocol designed to use in Windows operating systems over a network; Port 445: Used by newer versions of SMB (after Windows 2000) on top of a TCP stack, allowing SMB to communicate over the Internet. This also means
In addition to disabling NetBIOS on the NIC of each computer and through DHCP and disabling LLMNR, the outbound NetBIOS and LLMNR traffic should be restricted on the host firewall of each system by blocking the NetBIOS protocol and TCP port 139 as well as the LLMNR UDP port 5355. This step can prevent any NetBIOS or LLMNR traffic from accessing
NetBIOS allows computers and applications to communicate with network hardware, and allow data to be transmitted properly over a network. For example, Microsoft Windows computers that are named in a workgroup and not a domain use NetBIOS names, which are converted to IP addresses. NetBIOS commonly communicates on ports 137, 138, and 3 SMB revisited. If used over NetBIOS see above. If used native (port 445/port), each SMB message is preceded by a shim NetBIOS 'session message' prefix (type 0x00, 4 bytes long, includes the length of the message). Presumably this is required to specify the length of the message. A Wireshark capture listening on UDP port 137 will show NetBIOS Name Query packets. This capture will help you verify if NetBIOS traffic is still present on your network, and identify the source of the queries. Disabling NetBIOS can (and should) be accomplished from both sides of the client/server model. Two applications start a NetBIOS session when one (the client) sends a command to "call" another client (the server) over TCP Port 139. What is Port 139 used for. NetBIOS on your WAN or over Hence by blocking port 137 and 139 admin has added a security level that will prevent NetBIOS session service as well as NetBIOS name service for NetBIOS enumeration. Mainly in many organization, port series from 135 to 139 are blocked in the network for security reasons, therefore port 445 is used for sharing data in the network. Firewall: Block ports 135-139 plus 445 in and out. These are used by hackers to steal your info and take control of your pc and after doing so will use NetBIOS to then use your computer to take over another, etc, etc.. Port 137-139 is for Windows Printer and File Sharing but also creates a security risk if unblocked.