- Patch VPN gateways quickly: they are a top initial access target.
- Use certificates or MFA rather than shared secrets.
- Investigate unexpected tunnels and proxies: they are also attacker tools.
Port 16666: Vidder Tunnel Protocol
Port 16666 is assigned by IANA to vtp (Vidder Tunnel Protocol).
16666
How vtp works
VPN, tunnels & proxiesTraffic is wrapped in a tunnel between the two ends, so the network in between only sees the tunnel.
- Transport
- UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- VPN, tunnels & proxies
Is port 16666 dangerous?
We have no specific security note for port 16666. Its risk depends on the program actually listening on it. General advice for vpn, tunnels & proxies services:
IANA registry entries for port 16666
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| vtp | 16666 | UDP | Vidder Tunnel Protocol | - | 2011-10-24 |
| - | 16666 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 16666, and is it reachable?
Linux
sudo ss -ltnup 'sport = :16666' # process listening on 16666
sudo lsof -nP -i :16666macOS
sudo lsof -nP -i :16666
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 16666 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 16666 netstat -ano | findstr :16666
From another machine
nmap -p 16666 -sV <host> sudo nmap -sU -p 16666 <host> nc -zv <host> 16666
Block it in the firewall
sudo ufw deny 16666/udp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 16666" -Direction Inbound -LocalPort 16666 -Protocol UDP -Action Block # Windows
What is port 16666 used for?
Port 16666 is assigned by IANA to vtp (Vidder Tunnel Protocol).
Is port 16666 TCP or UDP?
Port 16666 is registered for UDP.
Is it safe to open port 16666?
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. Patch VPN gateways quickly: they are a top initial access target.
How do I check if port 16666 is open?
On Linux run "ss -ltnup 'sport = :16666'", on macOS "lsof -nP -i :16666", and on Windows "netstat -ano | findstr :16666" to see the local process. From another machine, "nmap -p 16666 <host>" shows whether it is reachable.