Port 445 (TCP) — SMB Direct File Sharing
Server Message Block (SMB) provides Windows file shares, NAS storage mounting, and Active Directory SYSVOL/Group Policy distribution across enterprise LANs.
| Port Number | 445 |
|---|---|
| Transport Protocol | TCP |
| Primary Service | SMB Direct File Sharing |
| Standard / Specification | MS-SMB2 / SMB3 |
| IANA Port Range | Well-Known System Port (0–1023) |
| Internet Exposure Risk | Extreme ransomware & worm target; NEVER expose TCP/445 to the public internet. |
Firewall Architecture & Hardening Best Practices
Unconditionally block inbound and outbound TCP/445 at ISP and perimeter firewalls. Require SMBv3 encryption inside private subnets or tunnel remote access over WireGuard/IPsec.
Operational Troubleshooting Note
Many residential and enterprise ISPs drop TCP/445 transit traffic upstream; mount cloud file shares over VPN or SMB-over-QUIC where supported.
Quick CLI Connectivity & Firewall Reference
# Test TCP/445 reachability (Linux / macOS / PowerShell) nc -zv target.example.com 445 Test-NetConnection -ComputerName target.example.com -Port 445 # Allow restricted CIDR on Linux UFW firewall ufw allow from 10.0.0.0/8 to any port 445 proto tcp
Planning firewall allowlists or VPN overlays? Use our IPv4 CIDR Calculator, MTU & TCP MSS Calculator, or WireGuard AllowedIPs Generator.
Browse Common Network & Cloud Ports
Port 22 (SSH) Port 25 (SMTP Mail Relay) Port 53 (Domain Name System) Port 67 (DHCPv4 Server) Port 80 (HTTP Web Traffic) Port 123 (Network Time Protocol) Port 161 (SNMP Polling) Port 179 (Border Gateway Protocol) Port 389 (LDAP Directory) Port 443 (HTTPS & HTTP) Port 445 (SMB Direct File Sharing) Port 465 (SMTPS Implicit TLS Submission) Port 500 (IPsec IKEv2 Key Exchange) Port 514 (Syslog Telemetry) Port 587 (SMTP Mail Submission) Port 636 (LDAPS) Port 853 (DNS over TLS) Port 993 (IMAPS Encrypted Mailbox) Port 1194 (OpenVPN Tunnel) Port 1433 (Microsoft SQL Server) Port 1812 (RADIUS Authentication) Port 2049 (Network File System) Port 2379 (etcd Client API) Port 3306 (MySQL & MariaDB) Port 3389 (Remote Desktop Protocol) Port 4500 (IPsec NAT Traversal) Port 5432 (PostgreSQL Database) Port 6379 (Redis) Port 6443 (Kubernetes API Server) Port 51820 (WireGuard VPN)