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// Other services

Port 4690: Prelude IDS message proto

Port 4690 is assigned by IANA to prelude (Prelude IDS message proto).

4690

How prelude works

Other services
client:4690preluderesponse client:4690preluderesponse

The client sends a request to port 4690 and the prelude 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 4690 dangerous?

We have no specific security note for port 4690. 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 4690

ServicePortTransportDescriptionReferenceUpdated
prelude 4690 TCP, UDP Prelude IDS message proto - 2005-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 4690, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4690'      # process listening on 4690
sudo lsof -nP -i :4690

macOS

sudo lsof -nP -i :4690

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4690 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4690
netstat -ano | findstr :4690

From another machine

nmap -p 4690 -sV <host>
sudo nmap -sU -p 4690 <host>
nc -zv <host> 4690

Block it in the firewall

sudo ufw deny 4690/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4690" -Direction Inbound -LocalPort 4690 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4690 used for?

Port 4690 is assigned by IANA to prelude (Prelude IDS message proto).

Is port 4690 TCP or UDP?

Port 4690 is registered for TCP and UDP.

Is it safe to open port 4690?

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 4690 is open?

On Linux run "ss -ltnup 'sport = :4690'", on macOS "lsof -nP -i :4690", and on Windows "netstat -ano | findstr :4690" to see the local process. From another machine, "nmap -p 4690 <host>" shows whether it is reachable.

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