Port 3024: Unassigned — The Squatter's History

What Port 3024 Is

Port 3024 sits in the registered port range (1024–49151). IANA manages this range and assigns ports to services that apply — but port 3024 has no official assignment. It is unregistered, unclaimed, and available.

That doesn't mean it's unused.

The Registered Port Range

Ports 1024–49151 were originally set aside for applications that needed a consistent, predictable port without requiring root privileges to bind (unlike ports below 1024, which require elevated access on Unix systems). IANA maintains a registry so services can stake a claim and avoid collisions.

Port 3024 never filed that claim. Which means it's been available for anyone to use — and some have.

Who Has Used Port 3024

WinCrash (late 1990s)

The first notable occupant was WinCrash, a Windows remote-access trojan that used TCP port 3024 as its command-and-control channel. WinCrash could log keystrokes, steal passwords, scan networks, and accept remote commands — the standard toolkit of late-1990s malware targeting Windows 95, 98, ME, and NT systems.¹

It's worth naming what this was: a backdoor. The attacker installed it, opened port 3024, and waited for a connection home. The port itself did nothing wrong — it was just the address where the malware answered the phone.

These systems are long obsolete. WinCrash as a threat is a footnote, not a risk.

Teleport (present day)

The more current occupant is Teleport, an open-source infrastructure access platform. In its default configuration, Teleport uses port 3024 as the SSH reverse tunnel listening address (tunnel_listen_addr).²

The reverse tunnel is the clever part. Instead of requiring every server to expose an inbound port to the Internet, Teleport agents establish outbound connections to the proxy on port 3024. The proxy holds the tunnel open. When a user wants to connect to a server behind a firewall, the traffic flows back through that already-established tunnel — no firewall rules to open, no exposed inbound ports on the target machine.

Port 3024 chosen for this: a consequence of Teleport's defaults, not any official designation.

How to Check What's on Port 3024

If port 3024 is open on a machine you're responsible for, find out what's listening:

macOS / Linux:

# Show what process is listening on port 3024
sudo lsof -i :3024

# Or with ss (Linux)
sudo ss -tlnp | grep 3024

Windows:

# Show listening ports with owning process IDs
netstat -ano | findstr :3024

# Then identify the process by PID
tasklist | findstr <PID>

If you see Teleport, you're probably fine. If you see something you don't recognize, investigate before assuming.

Why Unassigned Ports Matter

The port number system only works because most services respect the registry. When IANA assigns port 443 to HTTPS, every firewall, every tool, every network engineer in the world knows what traffic on port 443 probably means.

Unassigned ports break that legibility. When a port has no registered owner, you can't know from the number alone what's running. You have to check. That's not a flaw in the system — it's the honest consequence of having more ports than services. The registered range has 48,128 possible ports. There aren't 48,128 services worth registering.

Port 3024 is just one of thousands of honest gaps in the registry. The gap isn't dangerous. Not knowing what's in the gap is.