Port / TCP
9000PHP-FPM / MinIO / SonarQube
A heavily overloaded port: the PHP-FPM FastCGI listener, MinIO's S3 API, SonarQube, and Portainer all default to it.
If it is internet-facing: Finding 9000 open to the internet is a finding in its own right — it warrants an explanation, not just a rule.
Exposure
Localhost only
Transport
Cleartext
Risk if public
High
Exposure verdict
Port 9000 should be bound to 127.0.0.1. Nothing outside the host needs to reach it, and binding to 0.0.0.0 is the single change that turns it into an incident.
Traffic crosses the network readable and modifiable. Anything sensitive on this port needs a tunnel, a VPN, or a different protocol.
Registered with IANA on request, but bindable by any unprivileged user. Registration records intent — it does not reserve the port, so collisions between products are common.
Grouped with the other web & proxies ports so a rule written for one can be checked against its neighbours.
What actually goes wrong
2 notes- An exposed FastCGI listener accepts requests that can execute arbitrary PHP — it must never leave the host.
- Identify the owning process first; the correct exposure differs completely between FastCGI and an S3 API.
Recommended firewall rule
Deny at the edge and bind to loopback
A firewall rule is the second line here. Fix the bind address in the service configuration so the listener never leaves the host.
ufw
sudo ufw deny 9000/tcpiptables
sudo iptables -A INPUT -p tcp --dport 9000 -j DROPIf you do need it open to everyone
sudo ufw allow 9000/tcpWrite down why. An unexplained allow rule outlives the person who added it, and the next reviewer has no way to tell a deliberate exception from an accident.
Check what is really there
Listening locally
sudo ss -tlpn 'sport = :9000'The bind address is the answer that matters: 127.0.0.1 is local-only, 0.0.0.0 and :: mean every interface.
Listening (macOS)
sudo lsof -nP -iTCP:9000 -sTCP:LISTENmacOS ships lsof rather than ss; this names the owning process and user.
From outside
nmap -sV -Pn -p 9000 <host>A version probe confirms whether PHP-FPM / MinIO / SonarQube is actually what answers, rather than trusting the number. Only scan hosts you are authorised to test.
Reachability
nc -vz <host> 9000The quick yes/no when you only need to know whether a path exists through the firewall.