Port 669: MeRegister — The ghost town port

Port 669 sits in the well-known ports range (0-1023), officially assigned by IANA to a service called "MeRegister."¹ If you've never heard of MeRegister, you're not alone. Almost no documentation exists about what this service actually does or did. It's a ghost town in the port registry—officially claimed but practically abandoned.

What the Port Was Supposed to Do

IANA lists port 669 as assigned to MeRegister for both TCP and UDP.¹ That's essentially the extent of publicly available information. No RFCs define the protocol. No vendor documentation explains its purpose. No community of users discusses how to configure it.

The service appears to have been registered and then... forgotten. Whether it was a proprietary protocol that never gained adoption, an early experiment that was abandoned, or something else entirely remains unclear.

What the Port Actually Does (Sometimes)

Here's the uncomfortable truth: abandoned ports don't stay empty. Port 669 has been exploited by trojans including DP trojan and SniperNet.² When security scanners flag port 669, they're not warning that the port itself is malicious—they're warning that malware has used this port to communicate in the past.

This is what happens to ghost town ports. Someone officially claimed them decades ago, but nobody's using them for their intended purpose. The door exists, it has a number, and if you leave it unlocked, something else might walk through.

Why This Matters

Port 669 represents a category of ports that many people don't think about: the officially assigned but effectively unused. They're not unassigned—IANA has them on record with a service name. But they're not actively used by any widespread legitimate service either.

This creates confusion:

• Network administrators see the official assignment and assume it's legitimate
• Security tools flag historical trojan activity and assume it's suspicious
• Both are partially right

The port has a legitimate assignment. The port has been exploited. These facts coexist.

Checking What's Using Port 669

If you want to see if anything is listening on port 669 on your system:

On Linux or macOS:

sudo lsof -i :669
# or
sudo netstat -tulpn | grep :669

On Windows:

netstat -ano | findstr :669

If something is listening, verify what it is. Given the port's history, any unexpected service on 669 deserves investigation.

The Well-Known Ports Range

Port 669 belongs to the well-known ports range (0-1023), which means it requires root or administrator privileges to bind to it on most systems. IANA manages these assignments to prevent conflicts between different services.

But assignment doesn't guarantee adoption. The registry contains hundreds of ports like 669—officially claimed, minimally documented, rarely used. They're artifacts of protocols that never found their audience, proprietary systems that died with the companies that created them, or early Internet experiments that got registered and then abandoned.

The Honest Assessment

If you're running MeRegister, you'd know it. If nothing on your network is supposed to be using port 669, and you see traffic on it, investigate. The official assignment provides no protection against misuse.

This is the reality of managing 1,024 well-known ports across decades of Internet history. Not every assignment becomes SSH. Not every protocol becomes DNS. Some ports just sit there, officially registered, mostly forgotten, occasionally exploited.

Port 669 is one of those ports. It has a name. It has an assignment. But what it doesn't have is a community of legitimate users keeping watch over it—and that makes it more dangerous than useful.