Subnet and PortsPort 3389: Remote Desktop
Microsoft Remote Desktop Protocol (registered as ms-wbt-server).
Registry entry
| Port | Protocols | Registered name | IANA description | Assignee | Reference | Note |
|---|---|---|---|---|---|---|
| 3389 | tcp, udp | ms-wbt-server | MS WBT Server | Jordan Marchese | n/a |
What it is used for
Microsoft Remote Desktop Protocol (registered as ms-wbt-server).
The risk
It is one of the most attacked ports, with password guessing and exploits.
What to do
Do not expose it. Use a VPN, network-level authentication and two-step verification.
In the registry
Port 3389 is a user port (1024 to 49151), a range where applications register their own numbers. The registry lists one service for this number. Its main entry is ms-wbt-server, "MS WBT Server", registered for tcp, udp.
How to find out whether it is open on your computer
On your own computer or server, ask the operating system which programs are listening for connections, and look for port 3389 in the list. If a program you do not recognise listens on it, find out what it is before you close it. From outside, test only networks that you own or have permission to test: scanning other people's networks can be treated as an attack.
Is port 3389 safe to leave open?
It depends on what is listening and who can reach it. Open only what you need, restrict by address where possible, keep the software updated, and use encryption and strong authentication. The advice above applies to this port.
Does the registered name prove what runs on port 3389?
No. Programs can use any port. The registry tells you what the number was reserved for.
This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.