Port 313: Magenta Logic — The Ghost in the Registry

Port 313 sits in the well-known ports range (0-1023) with an official IANA assignment to a service called "magenta-logic." The contact name is Karl Rousseau. Beyond that, the trail goes cold.¹²

What Lives Here (Officially)

According to IANA's service registry, port 313 is assigned for both TCP and UDP to "Magenta Logic."³ That's the official story. But there's no RFC defining the protocol. No documentation explaining what it does. No company website. No software packages using it. The registration exists, but the service has left almost no archaeological evidence on the Internet.

This is not uncommon for older well-known port assignments. In the early days of the Internet, port numbers were allocated with less scrutiny than they are today. Someone requested port 313 for Magenta Logic, received it, and then either never deployed the service widely or it disappeared without leaving much of a record.

The Malware Shadow

Port 313 has been flagged by security databases as having been used by trojans or viruses in the past.⁴⁵ This doesn't mean Magenta Logic itself was malicious—it means that at some point, malware authors used this port for command and control or backdoor access. Unassigned or rarely-used ports are attractive to malware precisely because they're unlikely to conflict with legitimate services.

If you see traffic on port 313 today, it's worth investigating. It's probably not Magenta Logic.

The Well-Known Ports Range

Port 313 belongs to the System Ports or Well-Known Ports range (0-1023).⁶ These ports are assigned by IANA and historically required privileged access to bind to on Unix-like systems. The idea was that only root could start services on these ports, providing a basic layer of trust.

Being in this range means port 313 was claimed early, during an era when port allocation was less formalized. Many ports in this range have similar stories—registered to services that have faded from memory, leaving only their port number behind like a tombstone.

How to Check This Port

To see if anything is listening on port 313 on your system:

# Linux/Mac
sudo lsof -i :313
sudo netstat -tulpn | grep :313

# Windows
netstat -ano | findstr :313

If something is listening and you don't recognize it, investigate. It's unlikely to be legitimate Magenta Logic traffic.

Why Ghost Ports Matter

Ports like 313 reveal something about the Internet's archaeology. The port number space is finite. Every assignment is permanent. Some ports—like 80 for HTTP or 443 for HTTPS—carry the weight of billions of daily connections. Others, like 313, carry mostly questions.

These ghost ports serve as a reminder that the Internet's infrastructure was built incrementally by real people making decisions with imperfect information. Some of those decisions faded into irrelevance. But the port numbers remain, allocated forever, little tombstones in the registry.

Related Ports

• Port 31337 — Famously used by Back Orifice malware, demonstrating how obscure ports attract malicious use
• Port 1-1023 — The well-known ports range, assigned by IANA