CyberHunter
LinkedIn profile - Bastien Cordier Email: contact@bastiencordier.pro
// Other services

Port 1821: donnyworld

Port 1821 is assigned by IANA to donnyworld (donnyworld).

1821

How donnyworld works

Other services
client:1821donnyworldresponse client:1821donnyworldresponse

The client sends a request to port 1821 and the donnyworld 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 1821 dangerous?

We have no specific security note for port 1821. 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 1821

ServicePortTransportDescriptionReferenceUpdated
donnyworld 1821 TCP, UDP donnyworld - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1821, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1821'      # process listening on 1821
sudo lsof -nP -i :1821

macOS

sudo lsof -nP -i :1821

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1821 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1821
netstat -ano | findstr :1821

From another machine

nmap -p 1821 -sV <host>
sudo nmap -sU -p 1821 <host>
nc -zv <host> 1821

Block it in the firewall

sudo ufw deny 1821/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1821" -Direction Inbound -LocalPort 1821 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1821 used for?

Port 1821 is assigned by IANA to donnyworld (donnyworld).

Is port 1821 TCP or UDP?

Port 1821 is registered for TCP and UDP.

Is it safe to open port 1821?

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 1821 is open?

On Linux run "ss -ltnup 'sport = :1821'", on macOS "lsof -nP -i :1821", and on Windows "netstat -ano | findstr :1821" to see the local process. From another machine, "nmap -p 1821 <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

Latest vulnerability news

All news