- Do not expose remote administration directly: use a VPN or a zero-trust access proxy.
- Require MFA or key-based authentication and lock out brute-force attempts.
- Log every login and alert on new source addresses.
Port 89: SU/MIT Telnet Gateway
Port 89 is assigned by IANA to su-mit-tg (SU/MIT Telnet Gateway).
89
How su-mit-tg works
Remote accessThe client opens a session to port 89: each command typed is sent to the server, which runs it and returns the output.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Well-known (0-1023)
- Category
- Remote access
Is port 89 dangerous?
We have no specific security note for port 89. Its risk depends on the program actually listening on it. General advice for remote access services:
IANA registry entries for port 89
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| su-mit-tg | 89 | TCP, UDP | SU/MIT Telnet Gateway | - | - |
// source: IANA service name and port number registry
Which program uses port 89, and is it reachable?
Linux
sudo ss -ltnup 'sport = :89' # process listening on 89
sudo lsof -nP -i :89macOS
sudo lsof -nP -i :89
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 89 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 89 netstat -ano | findstr :89
From another machine
nmap -p 89 -sV <host> sudo nmap -sU -p 89 <host> nc -zv <host> 89
Block it in the firewall
sudo ufw deny 89/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 89" -Direction Inbound -LocalPort 89 -Protocol TCP -Action Block # Windows
What is port 89 used for?
Port 89 is assigned by IANA to su-mit-tg (SU/MIT Telnet Gateway).
Is port 89 TCP or UDP?
Port 89 is registered for TCP and UDP.
Is it safe to open port 89?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Do not expose remote administration directly: use a VPN or a zero-trust access proxy.
How do I check if port 89 is open?
On Linux run "ss -ltnup 'sport = :89'", on macOS "lsof -nP -i :89", and on Windows "netstat -ano | findstr :89" to see the local process. From another machine, "nmap -p 89 <host>" shows whether it is reachable.
Other remote access ports
:22 SSH tcp · udp · sctp · moderate risk :3389 RDP tcp · udp · critical risk :23 Telnet tcp · udp · critical risk :5900 VNC tcp · udp · critical risk :5985 WinRM (HTTP) tcp · udp · high risk :5986 WinRM (HTTPS) tcp · udp · high risk :10000 Webmin tcp · udp · high risk :107 Remote Telnet Service tcp · udp