Port 3389 (TCP & UDP) — Remote Desktop Protocol (RDP)
Microsoft Remote Desktop Protocol provides graphical Windows desktop administration over TCP/3389 with optional UDP/3389 acceleration for interactive video and input.
| Port Number | 3389 |
|---|---|
| Transport Protocol | TCP & UDP |
| Primary Service | Remote Desktop Protocol (RDP) |
| Standard / Specification | MS-RDPBCGR |
| IANA Port Range | Registered User Port (1024–49151) |
| Internet Exposure Risk | Top brute-force & ransomware vector worldwide; NEVER expose raw 3389 to the internet. |
Firewall Architecture & Hardening Best Practices
Block public inbound 3389 completely on edge firewalls. Access Windows servers exclusively through WireGuard, Zero Trust IAP tunnels, Azure Bastion, or an MFA-enforced RD Gateway on HTTPS/443.
Operational Troubleshooting Note
Always keep Network Level Authentication (NLA) enabled so unauthenticated sessions cannot spawn full Windows login screens.
Quick CLI Connectivity & Firewall Reference
# Test TCP/3389 reachability (Linux / macOS / PowerShell) nc -zv target.example.com 3389 Test-NetConnection -ComputerName target.example.com -Port 3389 # Inspect local UDP/3389 socket binding on Linux ss -uapn | grep :3389 # Allow restricted CIDR on Linux UFW firewall ufw allow from 10.0.0.0/8 to any port 3389 proto any
Planning firewall allowlists or VPN overlays? Use our IPv4 CIDR Calculator, MTU & TCP MSS Calculator, or WireGuard AllowedIPs Generator.
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