TCP port 445 is a network port used primarily by Microsoft’s Server Message Block (SMB) protocol for direct file and printer sharing over the internet and local networks. Unlike older SMB versions that relied on NetBIOS over ports 137–139, SMB over port 445 enables more efficient and secure communication. Because it allows data to be shared between computers, port 445 is often targeted by cyber attackers, making it a focus for network security measures. Disabling or securing this port is recommended to reduce vulnerability to threats like ransomware.