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// Other services

Port 673: CIMPLEX

Port 673 is assigned by IANA to cimplex (CIMPLEX).

673

How cimplex works

Other services
client:673cimplexresponse client:673cimplexresponse

The client sends a request to port 673 and the cimplex 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 673 dangerous?

We have no specific security note for port 673. 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 673

ServicePortTransportDescriptionReferenceUpdated
cimplex 673 TCP, UDP CIMPLEX - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 673, and is it reachable?

Linux

sudo ss -ltnup 'sport = :673'      # process listening on 673
sudo lsof -nP -i :673

macOS

sudo lsof -nP -i :673

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 673 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 673
netstat -ano | findstr :673

From another machine

nmap -p 673 -sV <host>
sudo nmap -sU -p 673 <host>
nc -zv <host> 673

Block it in the firewall

sudo ufw deny 673/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 673" -Direction Inbound -LocalPort 673 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 673 used for?

Port 673 is assigned by IANA to cimplex (CIMPLEX).

Is port 673 TCP or UDP?

Port 673 is registered for TCP and UDP.

Is it safe to open port 673?

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 673 is open?

On Linux run "ss -ltnup 'sport = :673'", on macOS "lsof -nP -i :673", and on Windows "netstat -ano | findstr :673" to see the local process. From another machine, "nmap -p 673 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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