CyberHunter
Local dataset, no network
// Other services

Port 166: Sirius Systems

Port 166 is assigned by IANA to s-net (Sirius Systems).

166

How s-net works

Other services
client:166s-netresponse client:166s-netresponse

The client sends a request to port 166 and the s-net service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Other services
01 Security

Is port 166 dangerous?

We have no specific security note for port 166. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 166

ServicePortTransportDescriptionReferenceUpdated
s-net 166 TCP, UDP Sirius Systems - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 166, and is it reachable?

Linux

sudo ss -ltnup 'sport = :166'      # process listening on 166
sudo lsof -nP -i :166

macOS

sudo lsof -nP -i :166

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 166 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 166
netstat -ano | findstr :166

From another machine

nmap -p 166 -sV <host>
sudo nmap -sU -p 166 <host>
nc -zv <host> 166

Block it in the firewall

sudo ufw deny 166/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 166" -Direction Inbound -LocalPort 166 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 166 used for?

Port 166 is assigned by IANA to s-net (Sirius Systems).

Is port 166 TCP or UDP?

Port 166 is registered for TCP and UDP.

Is it safe to open port 166?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 166 is open?

On Linux run "ss -ltnup 'sport = :166'", on macOS "lsof -nP -i :166", and on Windows "netstat -ano | findstr :166" to see the local process. From another machine, "nmap -p 166 <host>" shows whether it is reachable.

05 Related
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