SMB Port Numbers: A Guide to Optimizing and Securing Your Network

This guide explains SMB port usage (ports 139 and 445), the shift from NetBIOS to direct SMB over TCP/IP, associated security risks (notably exploitation by ransomware like WannaCry), and recommends mitigations such as disabling SMBv1, blocking SMB exposure to the internet, keeping systems patched, using VPNs for remote access, and optimizing performance via SMBv3 and SMB Direct.