Port 10407 — Unassigned, Yet Known

What This Port Is (And Isn't)

Port 10407 has no official service assigned by IANA. It falls within the registered port range (1024-49151)—numbers reserved for applications and services that have gone through IANA's assignment process. Most of these ports have clear owners: Slack uses 443 for HTTPS, Postgres claims 5432, Redis takes 6379. Port 10407 does not. It's vacant real estate on the port number line.

Why You've Heard Of It

The sole context where port 10407 appears is as a Nessus vulnerability scanner plugin ID (10407).¹ The plugin's name: "X Server Detection." Its job: identify whether a system is running an X11 display server and flag it as a security risk.

This is the port's only documented significance—not because it listens on that number, but because a security vendor's database indexed their detection code that way.

The Real Port: X11 At 6000-6063

The actual X Window System (the graphical framework for Unix/Linux) listens on ports 6000-6063.² The display number maps simply: your first display lives at port 6000, your second at 6001, and so on. X11 predates modern security practices by decades. Its protocol sends everything unencrypted over the network. Any client that can reach port 6000 can see all keystrokes, window contents, everything.³

Nessus scanning port 10407's assignment range doesn't find X11 servers there. The plugin ID just happened to be assigned that number in Nessus's internal database.

How To Check What's Listening

On Linux or macOS, see what's actually listening on any port:

# Show all listening TCP ports with process names
sudo lsof -i -P -n | grep LISTEN

# Or using netstat/ss (varies by OS)
netstat -tuln | grep LISTEN
ss -tuln | grep LISTEN

Windows equivalent:

netstat -ano | findstr LISTENING

These commands show real processes on real ports. Not plugin IDs. Not IANA assignments. Actual network listeners.

Why Unassigned Ports Matter

The 48,000-port registered range has room for perhaps 40,000 actual service assignments. The IANA registry contains roughly 5,000 assigned ports. That leaves 35,000+ ports that could be assigned but aren't.

This abundance of unassigned space is why the Internet still works. It's why your application can claim port 8080 without asking permission. It's why IoT devices, embedded systems, and one-off applications have somewhere to live.

But it also means port numbers can acquire meaning through accident, convention, or vendor adoption without official blessing. Port 10407 became "X Server Detection" not through IANA governance, but through Nessus' internal taxonomies.

The number itself is empty. The meaning we pour into it is optional.

Related Ports

• Port 6000-6063 — The actual X11 display server range
• Port 22 — SSH, the secure replacement for X11 forwarding
• Port 443 — HTTPS, the encrypted protocol X11 never had