Port 2533: SnifferServer — A Registered Port from Enterprise Software's Past

What This Port Is

Port 2533 sits in the registered ports range — 1024 through 49151. IANA formally assigned it to a service called SnifferServer, the server component of the Sniffer family of commercial network analyzers made by Network Associates, Inc. (NAI).

The IANA registry lists contact for this registration as Amy Weaver, and the port is registered for both TCP and UDP. ¹

The Product Behind It

Network Associates (formerly Network General Corporation) made the Sniffer, one of the earliest and most widely used commercial protocol analyzers. In the 1990s, the Sniffer was a dominant tool for network engineers — a specialized appliance or workstation that captured and decoded network traffic in real time. ²

The "Server" component would have run on a central collection point, with distributed probes sending captured data back to it. Port 2533 was how those components talked to each other.

Network Associates was eventually acquired by McAfee. The Sniffer product line was absorbed, rebranded, and ultimately discontinued. The port registration stayed in the IANA database, as these things do.

Observed Unofficial Uses

Security researchers have documented that Alcatel PBX systems use port 2533 to transmit CDR (Call Detail Record) data over TCP/IP — logging telephone call metadata from a private branch exchange to a collection server. ³

Some older threat databases also flag this port as having been used by malware for command-and-control traffic, though this reflects opportunistic reuse rather than any specific association with the port. Malware picks available ports; unrecognized port numbers are useful cover.

Why Unassigned-in-Practice Ports Exist

The registered ports range has over 48,000 slots. IANA assigns them on request, but has no mechanism to reclaim them when products are discontinued, companies are acquired, or software goes unmaintained. The result: thousands of ports that are technically registered but effectively dormant.

Port 2533 is one of them — officially owned, practically unclaimed.

How to Check What's Listening on This Port

If you see port 2533 active on a system and don't know why, these commands will tell you what process opened it:

Linux / macOS:

# Show process listening on port 2533
ss -tlnp sport = :2533

# Alternative with lsof
lsof -i :2533

Windows:

:: Show listening processes with port 2533
netstat -aon | findstr :2533

:: Then look up the PID
tasklist /fi "PID eq <pid>"

If nothing is listening, the port is just dormant — a number with a history and no current tenant.