Port 1413: Innosys-ACL — The ghost in the registry

Port 1413 is registered to a service called "Innosys-ACL" in the official IANA registry.¹ But if you search for what that actually means, you'll find almost nothing. No documentation. No active use. No company website explaining what it does.

This is what a ghost port looks like.

What the Registry Says

According to IANA, port 1413 is assigned to "Innosys-ACL"—presumably an access control list (ACL) service developed by a company called Innosys.² The registration exists for both TCP and UDP, suggesting it was intended as a real protocol at some point.

ACL systems manage permissions—who can access what, which operations are allowed, which are denied. In theory, Innosys-ACL would have been a network service that handled these access control decisions remotely. In practice, we have no evidence anyone ever used it.

The Registered Ports Range

Port 1413 sits in the registered ports range (1024–49151). This is the middle tier of the port system:

• Well-known ports (0–1023): Reserved for fundamental Internet services like HTTP, DNS, SSH
• Registered ports (1024–49151): Assigned by IANA to specific services upon request
• Dynamic/ephemeral ports (49152–65535): Used temporarily by client applications

Getting a port registered doesn't require proof the service works, or that anyone will use it. It just requires filing paperwork with IANA. Once registered, the port stays in the registry even if the service disappears.

Why Ghost Ports Exist

The registered ports range is full of entries like this. Companies register ports for protocols they're developing. Some of those protocols launch successfully. Many don't. Some companies go out of business. Some products get discontinued. Some ideas just never gain traction.

But the port registration remains. Port 1413 is reserved for Innosys-ACL whether or not Innosys-ACL exists anymore.

This creates an interesting problem: the registry has thousands of registered ports, but many of them aren't actually used for anything. They're just names attached to numbers, waiting for traffic that never comes.

What's Actually Listening

If you find port 1413 open on a system, it's probably not Innosys-ACL. More likely scenarios:

• A developer chose port 1413 arbitrarily for a custom application
• Malware picked a random registered port to avoid looking suspicious
• An administrator explicitly configured something to use this port

You can check what's listening on port 1413 with standard tools:

Linux/macOS:

sudo lsof -i :1413
sudo netstat -tuln | grep 1413

Windows:

netstat -ano | findstr :1413

If something is listening, the output will show which process opened the port. That tells you what's actually running, regardless of what the registry says the port is "for."

Why Unassigned Ports Matter

The existence of ghost ports like 1413 highlights an important truth: port numbers are just conventions.

Nothing stops you from running SSH on port 1413 instead of port 22. Nothing stops you from running your own custom service on any port you want. The registry is a coordination mechanism—a way to avoid collisions between popular services.

But for obscure registered ports that no one uses? The number is available in practice, even if it's reserved in theory. This is why system administrators sometimes choose random registered ports for internal services. The official assignment doesn't matter if no one's using it.

The ghost ports are a reminder that the Internet's infrastructure isn't perfectly planned. It's accumulated over decades. Some parts are actively maintained. Some parts are forgotten. And some parts—like port 1413—just exist in a strange limbo, registered but unused, official but irrelevant.