Port 2791: MT Port Registrator — Registered, Unknown

What This Port Is

Port 2791 sits in the registered port range (1024–49151), the middle tier of the port numbering system. IANA lists it under the service name mtport-regist, assigned to something called "MT Port Registrator" on both TCP and UDP.

That's where the trail ends.

There is no public RFC, no vendor documentation, no open-source project, no forum post explaining what MT Port Registrator does or who built it. The registration exists. The service, as far as the public Internet is concerned, does not.

What the Registered Range Means

The three port ranges each tell a different story:

Port 2791 is a registered port, meaning someone filed a request with IANA to claim it. The process is straightforward: you submit a form, describe your service, and IANA records it. There's no ongoing obligation to maintain, document, or actually use the port. Registrations don't expire.

The result is a registry that contains thousands of entries like this one — names without implementations, services that may have launched and died, or internal tools that were registered but never shipped.

Any Known Unofficial Uses

Some security databases have flagged port 2791 as occasionally associated with malware activity — meaning threat actors have used it for command-and-control traffic at some point.¹ This is not specific to port 2791; any unmonitored registered port with no legitimate traffic can become convenient cover for malicious use. The absence of known legitimate traffic makes anomalies harder to notice.

The port range 2700–2800 has also been loosely associated with KnowShowGo, an obscure P2P application from the early 2000s, though this association is informal and not reflected in the IANA registry.²

How to Check What's Listening on This Port

If you see traffic on port 2791 and want to know what's causing it:

On Linux or macOS:

# Show which process is listening on port 2791
sudo ss -tlnp sport = :2791

# Or with lsof
sudo lsof -i :2791

On Windows:

netstat -ano | findstr :2791

Then cross-reference the process ID (PID) against Task Manager or tasklist to identify the program.

If nothing legitimate on your system should be using this port and you see active connections, that's worth investigating.

Why Unassigned and Ghost Ports Matter

The port registry is not a living system — it's more like a ledger. Once something is written in, it stays. This means the registered range contains ports that are actively used, ports registered but never deployed, and ports whose registrants have long since disappeared.

From a security standpoint, that ambiguity is useful to attackers. Traffic on a well-known port (80, 443) gets scrutinized. Traffic on an obscure registered port with no known legitimate service is easy to overlook.

Understanding that a port's IANA status and its actual behavior in the wild are two separate questions is foundational to reading network traffic honestly.