Port 3434: OpenCM Server — A Registered Port Nobody's Home

What Port 3434 Is

Port 3434 sits in the registered port range (1024–49151). These ports are assigned by IANA upon request from software projects and vendors. Unlike the well-known ports below 1024, no special privileges are required to open a registered port — any process can bind to 3434 without administrator access.

IANA assigned port 3434 to OpenCM Server (opencm) around March 2002.¹ OpenCM was an open-source configuration management system — a tool for tracking software components, versions, and changes across a development environment. The project registered the port, presumably deployed a server component that listened on it, and then largely disappeared from the public Internet.

Today, port 3434 is one of many ghost registrations in the IANA database: officially claimed, practically absent. Most port reference databases list it as unassigned or unknown, which is technically incorrect but practically accurate — you will not encounter OpenCM Server in the wild.

Security History

In 2003, a trojan called Backdoor.Slao used port 3434 to establish unauthorized remote access to infected Windows machines.² The malware predated widespread awareness of this port, likely choosing it precisely because it was obscure. Backdoor.Slao is a 20-year-old threat and is not a current concern, but its association with this port is documented in security databases.

If you see unexpected traffic on port 3434, it is not Backdoor.Slao — it is almost certainly a development server, a custom application, or misconfigured software that happened to land on this port.

Common Unofficial Uses

Port 3434 has no dominant unofficial use. Developers sometimes land here when:

• A default port (like 3000 or 3333) is already occupied and the next available port gets picked automatically
• A configuration file hardcodes an arbitrary high port for a local service
• Tunneling or proxy software selects ports dynamically from this range

Without context, an open port 3434 tells you nothing about what's running. You have to ask.

What to Do If You See Port 3434 Open

On Linux or macOS

# Show which process is listening on port 3434
sudo lsof -i :3434

# Alternative using ss (modern Linux)
sudo ss -tlnp | grep 3434

On Windows

# Show process and PID bound to port 3434
netstat -ano | findstr :3434

# Look up the PID in Task Manager, or:
Get-Process -Id <PID>

The output will tell you the process name and path. That is your answer — not the port number.

Why Unassigned (and Ghost) Ports Matter

The port registry exists to prevent collisions. When two applications both try to listen on the same port, one of them fails. Registrations are supposed to be reservations.

But IANA does not enforce registrations, revoke them for abandoned projects, or confirm that registered services still exist. The registry reflects intent, not reality. Port 3434's registration is technically valid; the service it references is effectively gone.

This matters for firewall rules and network monitoring. Blocking or alerting on "unregistered" ports misses ghost registrations like this one. Blocking or alerting on "registered" ports might flag legitimate local development servers that happened to land on a dormant registration. The only reliable signal is: what process is actually bound to this port on your system, right now?