Port 578: ipdd — The mystery tenant

Port 578 sits in the well-known ports range (0-1023), officially assigned by IANA to a service called "ipdd."¹ The problem? No one can tell you what ipdd actually is.

The Ghost Service

According to IANA's registry, port 578 is assigned to "ipdd" for both TCP and UDP.² The description field? Also "ipdd." No RFC. No documentation. No protocol specification anyone can find.

This isn't uncommon in the port registry. Sometimes a service gets assigned a port number, then disappears. The company goes under. The protocol gets abandoned. The project never launches. What remains is a number in a database—a nameplate on a door that no one opens anymore.

What Moved In

When a port sits unused, other things move in. Security databases flag port 578 as a former trojan port—malware has used it in the past to communicate.³ This doesn't mean a virus is currently using port 578, but it means someone noticed suspicious traffic here and documented it.

This is the lifecycle of abandoned ports. The original tenant leaves. The space sits empty. Eventually something else—usually something unwelcome—moves in.

Checking What's Listening

To see if anything is actually using port 578 on your system:

Linux/Mac:

sudo lsof -i :578
sudo netstat -tulpn | grep :578

Windows:

netstat -ano | findstr :578

If something is listening on port 578 and you don't know what it is, that's worth investigating. Legitimate services rarely use this port because there's no standard protocol running here.

Why Mystery Ports Matter

Port 578 represents a strange corner of the Internet's infrastructure. The well-known ports range (0-1023) is supposed to be the organized, documented section—ports with clear purposes and defined protocols.

But even here, you find mysteries. Ports assigned to services that may never have existed publicly. Names without explanations. Numbers without stories.

These gaps matter because security depends on knowing what should be running where. When a port has no known legitimate use, any activity becomes suspicious. The absence of a story makes the port more dangerous, not less.

The Registry Entry

IANA maintains the official registry because someone has to keep track of the numbers. Port 578 has its entry: a service name, a protocol designation, a place in the list. Whether anyone ever actually used ipdd for its intended purpose—whatever that was—is a question the registry doesn't answer.

Some ports carry the weight of millions of connections. Some carry mysteries. Port 578 carries both a name and the absence of everything that should come with it.