Port 21 is used by File Transfer Protocol (FTP). File transfers between client and server. Sends credentials in plain text — largely replaced by SFTP.
What Does an Open Port 21 Mean?
A file transfer server is running. FTP on port 21 is a significant security risk if exposed to the internet — credentials travel unencrypted.
This port should NOT be open to the public internet on typical systems. If you see it open, investigate immediately.
Security Risk Level
High Risk
How to Check if Port 21 Is Open
Use the ExamineIP Port Scanner to check if port 21 is open on any IP address from the public internet. Enter the target IP and select the relevant port preset.
How to Close Port 21
- Stop the service using port 21 if you no longer need it
- Add a firewall rule blocking inbound connections on port 21
- Check your router for port forwarding rules that expose this port
- Run
netstat -ano | findstr :21(Windows) to see which process is using it
Related Ports
FTP is related to: {implode(‘, ‘, Array)}
Protect Your Open Ports
If you need services like remote access, use a VPN to create a private encrypted tunnel instead of exposing ports directly to the internet. A VPN also hides your real IP address so port scanners cannot identify your device. Try PureVPN or IPVanish.