Port 2568: Spamtrap — The Port That Was Reserved and Forgotten

What Port 2568 Is

Port 2568 sits in the registered port range (1024–49151), the middle tier of the port numbering system. This range is where organizations and developers can formally claim a port number from IANA for a specific service. The idea is to reduce collisions — if your application needs a well-known home on the network, you register a port so other services know to stay clear.

On August 29, 2008, someone did exactly that for port 2568. The registrant, Charles Bennett at Ohio University, claimed the name "spamtrap" with the description SPAM TRAP for both TCP and UDP.¹

And then, as far as anyone can tell, nothing else happened.

What a Spam Trap Actually Is

A spam trap is a lure — an email address or server deliberately left in the wild to catch spammers. Spammers harvest addresses from the Internet; spam trap operators put fake or expired addresses out there and wait. When email arrives at a trap address, it's almost certainly spam, because no real person gave that address out.

The concept is well-established and widely deployed. But it's deployed through normal email infrastructure — SMTP on port 25, mail servers, blocklists — not through a dedicated protocol running on its own port.

What protocol would a "spamtrap" service on port 2568 have spoken? Nobody seems to know. No RFC was ever published. No software appears to implement it. The registration exists. The protocol doesn't.

What's Actually Listening on This Port

Almost certainly nothing — unless you deliberately put something there.

If you're curious what's running on port 2568 on your own machine:

macOS / Linux:

lsof -i :2568

or

ss -tlnp | grep 2568

Windows:

netstat -ano | findstr :2568

If nothing comes back, the port is quiet. That's the expected result.

Why This Matters

Registered ports are supposed to represent active, real-world services. Most do. But the registry also contains artifacts like this — names claimed in good faith, maybe for a project that never shipped, or a protocol that never found adoption.

Port 2568 is a small monument to Internet intention. Someone had a plan for a spam trap protocol. They went through the official process. They got their port number. The protocol never materialized.

The port still waits.