Port 2940: SM-PAS-3 — A Name in the Registry

What Port 2940 Is

Port 2940 sits in the registered ports range (1024-49151), the middle tier of the port numbering system. These ports don't require root privileges to open, and they're nominally assigned by the Internet Assigned Numbers Authority (IANA) to specific services. The well-known ports below 1024 carry HTTP, SSH, SMTP — the backbone protocols the Internet runs on. Registered ports are the next tier out: more specialized, less universal.

Port 2940 is formally assigned to SM-PAS-3 in IANA's registry, supporting both TCP and UDP. ¹

What SM-PAS-3 Is

Honestly? Unknown.

SM-PAS-3 is the third in a series of five consecutive registrations occupying ports 2938 through 2942 (SM-PAS-1 through SM-PAS-5). The registrant listed is Tom Haapanen. There is no RFC defining the protocol. There is no public specification. There is no implementation anyone has written about.

The SM-PAS entries are what sometimes happens in the registered port space: someone secures a block of ports for a project that either never shipped, never needed its ports documented publicly, or quietly faded away. The name exists. The assignment exists. The protocol, if it ever existed in working form, left no public trace.

Security Note

Port scanners and some security databases flag port 2940 as having been used by trojans and backdoors over the years — the usual story for any obscure unoccupied port. ² Malware doesn't respect IANA assignments. It uses whatever port happens to be open and unmonitored.

If port 2940 is active on a system you control, and you don't know why, that's worth investigating.

How to Check What's Listening

On any system where port 2940 shows activity, these commands will tell you what's using it:

Linux / macOS:

# Show which process is listening on port 2940
ss -tlnp | grep 2940

# Or with lsof
lsof -i :2940

Windows:

# Show listening ports and associated process IDs
netstat -ano | findstr :2940

# Then look up the process by PID
tasklist | findstr <PID>

If nothing is listening, the port is idle — which is the normal state for SM-PAS-3 on essentially every machine on the Internet.

Why Unassigned-in-Practice Ports Matter

The registered port space has over 48,000 slots. Many carry real, active protocols. Many more are like port 2940 — assigned to something, assigned long ago, and now effectively unclaimed. This gap between assignment and use is why network monitoring matters.

A port that should be quiet and is loud is a signal worth reading.