Common attacks and weaknesses
- Query amplification and DDoS.
Port 27015: Steam / Source engine
Source engine game servers and Steam.
27015
How Steam / Source engine works
GamingThe game client and server exchange small updates many times per second over port 27015. It travels in clear text: anyone on the path can read it.
- Transport
- UDP · TCP
- Exposure risk
- 3/10 moderate if reachable from the Internet
- Encryption
- Clear textreadable on the network
- IANA status
- Unassignedcommon use differs from the registry
- Range
- Registered (1024-49151)
- Category
- Gaming
Is port 27015 dangerous?
How to secure it
- Rate-limit queries and keep servers updated.
Unofficial use. The IANA assignment below differs from what is usually found on this port in practice.
IANA registry entries for port 27015
No entry. The port is free for any application, so check what uses it on your hosts.
// source: IANA service name and port number registry
Which program uses port 27015, and is it reachable?
Linux
sudo ss -ltnup 'sport = :27015' # process listening on 27015
sudo lsof -nP -i :27015macOS
sudo lsof -nP -i :27015
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 27015 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 27015 netstat -ano | findstr :27015
From another machine
nmap -p 27015 -sV <host> sudo nmap -sU -p 27015 <host> nc -zv <host> 27015
Block it in the firewall
sudo ufw deny 27015/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 27015" -Direction Inbound -LocalPort 27015 -Protocol TCP -Action Block # Windows
What is port 27015 used for?
Source engine game servers and Steam.
Is port 27015 TCP or UDP?
Port 27015 is registered for UDP and TCP.
Is it safe to open port 27015?
It is rated 3/10 (moderate) when exposed to the Internet. Query amplification and DDoS. Rate-limit queries and keep servers updated.
How do I check if port 27015 is open?
On Linux run "ss -ltnup 'sport = :27015'", on macOS "lsof -nP -i :27015", and on Windows "netstat -ano | findstr :27015" to see the local process. From another machine, "nmap -p 27015 <host>" shows whether it is reachable.
Other gaming ports
:25565 Minecraft tcp · moderate risk :666 doom Id Software tcp · udp :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