Port 2233: Infocrypt — Assigned to Nothing

What Port 2233 Is

Port 2233 sits in the registered ports range (1024–49151). These ports are meant to be assigned to specific services by the Internet Assigned Numbers Authority (IANA) — the organization that keeps order in the port numbering system. Applications register here to claim a port number as their own, preventing conflicts with other software.

Port 2233 carries the service name "infocrypt" in port databases and registries. Both TCP and UDP are listed.

That's where the trail goes cold.

The Mystery of Infocrypt

No RFC documents infocrypt. No software package is known to use it. No company has claimed it. Security researchers who have looked at it over the years have found nothing. The name appears in port databases the way a name appears in an old phone book — present, but pointing to someone who either moved or never existed.

This happens more often than you'd expect. The IANA registry was less rigorous in earlier decades. Port numbers were assigned on request, sometimes with minimal documentation requirements, and some of those assignments belong to products that never shipped, companies that folded, or projects that simply evaporated.¹

Infocrypt is one of those. A registered name with no discoverable history.

The Trojan Connection

Port 2233 appears in historical trojan port lists — security databases from the early 2000s that flagged ports used by remote access trojans and malware. This doesn't mean the port itself is dangerous, and it doesn't mean any active threat currently uses it. Trojans picked ports somewhat arbitrarily, often choosing registered-but-unused ports precisely because they looked like legitimate traffic.²

If port 2233 shows up active on a system you don't control, it's worth investigating. On a system you do control, you should know what's there.

How to Check What's Listening on Port 2233

On Linux or macOS:

# Show the process listening on port 2233
ss -tlnp | grep 2233

# Or with lsof
lsof -i :2233

On Windows:

netstat -ano | findstr :2233

Take the process ID from the output and look it up:

# Linux/macOS
ps aux | grep <PID>

# Windows (Task Manager, or:)
tasklist | findstr <PID>

If something unexpected is listening on 2233 on a production system, that's worth understanding before moving on.

Why Unassigned (and Ghost-Assigned) Ports Matter

The port numbering system works because everyone agrees on what lives where. Port 443 is HTTPS. Port 22 is SSH. Port 53 is DNS. That shared agreement is what makes the Internet legible.

Ports like 2233 — assigned to nothing functional, documented by no one — represent gaps in that agreement. They're not dangerous in themselves. But they're reminders that the registry is a human artifact, built over decades, with the usual accumulation of dead entries and forgotten history.

The practical upshot: if you see traffic on port 2233 and can't explain it, the explanation isn't "it's the infocrypt service." There is no infocrypt service. Something else is using that port, and you should find out what.