Networking · Protocols
SMB
Server Message Block is the Windows file and printer sharing protocol, operating over TCP/445 in modern deployments.
FoundationalUpdated 2026-09-01
Overview
SMB 3.x adds encryption, signing, multichannel and directory leasing. It underpins Windows file services, roaming profiles, Group Policy delivery and many application installs.
SMB is also a primary lateral movement channel. Administrative shares, cached credentials and weak signing settings have made it central to ransomware propagation.
Security considerations
- Disable SMBv1 entirely and require signing; enable encryption for sensitive shares.
- Block SMB at the internet edge and restrict workstation to workstation SMB with host firewall rules.