- Keep game servers and their plugins updated.
- Rate-limit queries to limit DDoS amplification.
- Run game servers under an unprivileged account.
Port 666: doom Id Software
Port 666 is assigned by IANA to doom (doom Id Software), mdqs ().
666
How doom works
GamingThe game client and server exchange small updates many times per second over port 666.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned2 registered services
- Range
- Well-known (0-1023)
- Category
- Gaming
Is port 666 dangerous?
We have no specific security note for port 666. Its risk depends on the program actually listening on it. General advice for gaming services:
IANA registry entries for port 666
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| doom | 666 | TCP, UDP | doom Id Software | - | - |
| mdqs | 666 | TCP, UDP | - | - |
// source: IANA service name and port number registry
Which program uses port 666, and is it reachable?
Linux
sudo ss -ltnup 'sport = :666' # process listening on 666
sudo lsof -nP -i :666macOS
sudo lsof -nP -i :666
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 666 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 666 netstat -ano | findstr :666
From another machine
nmap -p 666 -sV <host> sudo nmap -sU -p 666 <host> nc -zv <host> 666
Block it in the firewall
sudo ufw deny 666/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 666" -Direction Inbound -LocalPort 666 -Protocol TCP -Action Block # Windows
What is port 666 used for?
Port 666 is assigned by IANA to doom (doom Id Software), mdqs ().
Is port 666 TCP or UDP?
Port 666 is registered for TCP and UDP.
Is it safe to open port 666?
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. Keep game servers and their plugins updated.
How do I check if port 666 is open?
On Linux run "ss -ltnup 'sport = :666'", on macOS "lsof -nP -i :666", and on Windows "netstat -ano | findstr :666" to see the local process. From another machine, "nmap -p 666 <host>" shows whether it is reachable.
Other gaming ports
:25565 Minecraft tcp · moderate risk :27015 Steam / Source engine udp · tcp · moderate risk :1926 Evolution Game Server tcp · udp :2346 Game Connection Port tcp · udp :2347 Game Announcement and Location tcp · udp :2348 Information to query for game status tcp · udp :2914 Game Lobby tcp · udp :3074 Xbox game port tcp · udp