Port 509 sits in the well-known ports range (0-1023), officially assigned by IANA to SNARE (System iNtrusion Analysis and Reporting Environment). But there's a problem: SNARE doesn't actually use port 509. It never has.
What Was Supposed to Happen
The Internet Assigned Numbers Authority maintains the official registry of port assignments. Port 509 appears in that registry, assigned to "snare" with Dennis Batchelder listed as the contact.1 Both TCP and UDP protocols were reserved.
SNARE is real software—a collection of tools for gathering audit logs from various systems and pushing them to central servers for analysis.2 It's used for security monitoring, intrusion detection, and compliance reporting. Organizations deploy it to watch what's happening across their networks.
What Actually Happened
When SNARE was built, it used port 6161 for agent communication, not port 509.3 The agents send their log data over port 6161 in native UDP or TCP format. For encrypted connections, SNARE uses port 6163. For syslog compatibility, it uses the standard port 514.
Port 509 appears nowhere in SNARE's actual architecture.
The Bureaucratic Ghost
This happens more often than you'd think. Someone files an application with IANA to reserve a port number during the planning phase of a project. The paperwork gets approved. The port gets assigned. Then during development, practical considerations intervene. Maybe port 6161 was already in use internally. Maybe the number was easier to remember. Maybe the original plan changed.
The software ships with different ports. But the IANA registry remains unchanged. Modifying a port assignment requires filing another form, and if the port isn't actually being used anyway, why bother? The registration sits there, a bureaucratic fossil, pointing to nothing.
Why This Matters
Port 509 is technically occupied but functionally empty. If you're scanning a network and see traffic on port 509, it's not SNARE. It might be:
- A different application using the port unofficially
- A misconfigured service
- Malicious traffic disguising itself
- Someone who read the IANA registry and assumed that's what SNARE uses
The gap between registry and reality creates confusion. Documentation says one thing, the software does another.
Checking Port 509
To see what's actually listening on port 509:
Linux/Mac:
Windows:
If you find something, it's not SNARE. Whatever is there claimed the port outside the official assignment.
The Well-Known Range
Port 509 falls within 0-1023, the well-known ports range. IANA carefully manages these assignments because they're reserved for system-level services. Getting a well-known port assignment requires demonstrating that your protocol serves a fundamental network function and needs the elevated privilege that these ports traditionally carry.
Someone made that case for SNARE. The port was granted. Then the software went a different direction.
The Lesson
The Internet's port registry is not a map of what exists. It's a record of intentions, some of which materialized and some of which didn't. Port 509 is assigned, but vacant. The nameplate is on the door, but nobody's home.
If you need log collection and intrusion analysis, SNARE exists and works. Just don't look for it on port 509.
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