Port 975: Unassigned (Unofficially SecureNet Pro)

Port 975 occupies an interesting position in the port number system: it's officially unassigned by IANA, yet it has a known unofficial use.

The Official Status

According to IANA (Internet Assigned Numbers Authority), ports 954-988 are designated as Unassigned.¹ This means:

• No service has officially registered port 975
• The port is available for assignment upon request
• IANA hasn't reserved it for any special purpose

Port 975 falls within the well-known ports range (0-1023). These ports require privileged access on Unix-like systems - you need root permissions to bind a service to them. This range was originally meant for core Internet services, but not every port in this range got claimed.

The Unofficial Reality

Despite its unassigned status, port 975 appears in network scanner databases as "securenetpro-sensor" or simply "securenet."² SecureNet Pro is a network intrusion detection system, and its sensors apparently listen on port 975.

This is common. The gap between official port assignments and what actually runs on networks is wider than you might think. Services claim ports without formal registration. Old assignments fade away but linger in databases. The port registry is descriptive, not prescriptive - it documents what should be there, not what is.

Why Unassigned Ports Matter

The existence of unassigned ports serves several purposes:

Room for growth - New protocols need port numbers. Unassigned blocks provide space for future services without having to reclaim ports from dead protocols.

Flexibility - Organizations can use unassigned ports for internal services without risking conflicts with well-known protocols. If you're running something that doesn't communicate beyond your network, an unassigned port works fine.

Testing and development - Developers testing new protocols need somewhere to listen. Unassigned ports provide that space without stepping on production services.

Checking What's Actually Listening

If you want to see what's actually using port 975 on your system, you have options:

On Linux or macOS:

# Using netstat
sudo netstat -tulpn | grep ':975'

# Using lsof
sudo lsof -i :975

# Using ss (modern replacement for netstat)
sudo ss -tulpn | grep ':975'

On Windows:

netstat -ano | findstr ":975"

The sudo prefix matters on Unix-like systems. Without root privileges, you'll see the port but not which process owns it.³

The Contradiction

Port 975 demonstrates something true about the Internet: official governance and actual practice don't always align. IANA says "unassigned." Nmap says "securenetpro-sensor." Both are correct, in their way.

The port sits empty in the official registry, waiting for someone to file paperwork. Meanwhile, SecureNet Pro sensors are out there listening on port 975, answering connections, doing their job. The Internet works because it's pragmatic, not because everyone follows the rules.