Port 1377 is officially registered to Cichlid License Manager, a software licensing service registered with IANA (Internet Assigned Numbers Authority). Both TCP and UDP versions of port 1377 are assigned to this service.12
But here's the reality: most people have never heard of Cichlid License Manager. The software exists, it has a registered port, but it's not exactly running on millions of machines. And that creates a problem.
The Ghost Town Problem
Port 1377 lives in the registered ports range (1024-49151)—the middle tier of the port number system. These ports are officially registered with IANA for specific services, unlike the well-known ports (0-1023) that run the Internet's core infrastructure, or the dynamic/ephemeral ports (49152-65535) that your operating system assigns on the fly.
The registered range contains about 48,000 port numbers. IANA has assigned thousands of them to specific applications and services. Some you've heard of. Most you haven't.
Cichlid License Manager is one of the ones you haven't heard of. And that's exactly what makes ports like 1377 attractive to attackers.
Why Unused Ports Matter
When a port is registered but rarely used, it becomes a digital ghost town. System administrators aren't monitoring it. Firewalls might not block it by default. Security tools aren't watching for unusual traffic patterns on it.
Port 1377 has been flagged in security databases as having been used by trojans and malware in the past.3 This doesn't mean the port is inherently malicious—it means that malware authors noticed nobody was watching it and moved in.
The same pattern plays out across thousands of registered ports. A company registers a port for their software. The software never becomes popular, or gets discontinued, or simply runs on so few systems that the port sits idle on most networks. And idle ports are useful to attackers.
What's Actually Running on Port 1377?
On your system, probably nothing. Unless you're running Cichlid License Manager (unlikely), port 1377 should be closed.
To check what's listening on port 1377:
On Linux or macOS:
On Windows:
If you see something listening and you don't recognize it, investigate. It could be legitimate software using an available port, or it could be something you didn't install.
The Registered Ports Range
Port 1377 sits in the middle of a range designed for legitimate applications that need consistent port numbers but aren't fundamental Internet infrastructure:
- Well-known ports (0-1023): Reserved for core services like HTTP (80), HTTPS (443), SSH (22). Requires administrative privileges to bind to these ports on most systems.
- Registered ports (1024-49151): Available for registration with IANA. Companies and developers can request specific port assignments for their applications. Port 1377 lives here.
- Dynamic/ephemeral ports (49152-65535): Temporary ports assigned by your operating system for outbound connections. Not assigned to specific services.
The registered range exists because many applications need stable, predictable port numbers. Database servers, game servers, enterprise software, specialized protocols—they all need to agree on a port number so clients know where to connect.
But registration doesn't mean usage. Thousands of registered ports sit unused on typical systems, creating opportunities for both legitimate software looking for an available port and malicious software looking to hide.
Security Implications
Port 1377 represents a broader security principle: obscurity is not security, but it is useful to attackers.
Legitimate services use well-known ports because they want to be found. Malware prefers obscure registered ports because it doesn't want to be noticed. A network administrator who sees unexpected traffic on port 443 (HTTPS) will investigate. The same administrator might not notice unexpected traffic on port 1377 because they don't know what's supposed to be there.
This is why good security practice includes:
- Default-deny firewalls: Block all ports except the ones you actually need
- Port scanning: Regular checks for unexpected listening services
- Monitoring outbound traffic: Not just what's coming in, but what's trying to get out
- Security baselines: Knowing what normally runs on your systems so you notice anomalies
Why This Port Exists
Someone at Cichlid needed a port number for their license management software. They went through the IANA registration process, got assigned port 1377, and documented it in the official registry. This is the system working as designed.
The problem isn't the registration system. The problem is that most registered ports are invisible until something goes wrong. Port 1377 is officially assigned, rarely used, and occasionally exploited—just like thousands of its neighbors in the registered range.
That's the ghost town problem. The ports exist. They're registered. They're documented. And on most networks, nobody's home.
Frequently Asked Questions About Port 1377
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