Port 676 sits in the well-known ports range (0-1023), officially assigned to something called "VPPS-Via." The problem? Nobody seems to know what VPPS-Via actually is.
What We Know
Port 676 is registered with IANA for both TCP and UDP.1 The registration lists the service name as "vpps-via" and attributes it to someone named Ulysses G. Smith Jr. from cesi.com. That's where the paper trail ends.
Search for VPPS-Via and you'll find the port listed in every registry database. Search for what VPPS-Via actually does, and you'll find nothing. No RFC. No protocol specification. No product documentation. Just a name in a registry that's been copied from database to database for years.
This is genuinely strange. Well-known ports below 1024 are supposed to be reserved for established, widely-used services—things like HTTP, SSH, and DNS. Port 676 has the official designation but none of the visibility.
The Well-Known Range
Ports 0-1023 are called "well-known ports" or "system ports." IANA assigns them through a rigorous review process for protocols that are expected to be deployed across the Internet.2 Getting a well-known port number is supposed to mean something—it's prime real estate in the port number space.
Port 676 has that designation, but the protocol it was assigned to seems to have disappeared into history.
Unofficial Uses
Like many ports without active official use, port 676 occasionally shows up in other contexts:
- ApplianceWare Server: Some sources indicate this application uses port 676 by default for SSL-encrypted communication3
- Mac OS X RPC services: Port 676 has been associated with NetInfo and other RPC-based services on older Mac systems4
These are unofficial uses—applications that happened to choose port 676 because it wasn't being actively used by its assigned protocol.
Security Considerations
Port 676 has been flagged in malware databases, not because the port itself is dangerous, but because some trojans have used it for command and control communication.5 This is common for ports that aren't actively monitored—if nobody expects legitimate traffic on port 676, malicious traffic is less likely to be noticed.
If you see unexpected traffic on port 676, investigate it. The obscurity of the official protocol means legitimate traffic on this port is rare.
Checking What's Listening
On Linux or Mac:
On Windows:
If something is listening on port 676, you probably want to know what it is and why it's there.
Why This Matters
Port 676 represents something interesting about Internet infrastructure: protocols can be officially registered, assigned scarce resources, and then fade into obscurity while their port assignments remain.
The well-known ports range is finite—only 1,024 numbers exist below port 1024. Port 676 occupies one of those slots, assigned to a protocol that may not have been used in decades (if it was ever widely deployed at all).
This raises questions about port number allocation. Should ports be reclaimed if the protocols they were assigned to are no longer active? How do we handle historical assignments when the documentation has been lost?
Port 676 is a ghost in the registry—officially recognized but practically unknown. Its designation is real. What it was supposed to do remains a mystery.
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