Port 21 · FTP Control

Port 21 is FTP Control, TCP.

FTP command and authentication channel. Unencrypted — use SFTP (22) or FTPS (990) instead.

Palo Alto

Create the service object for this port, then allow the App-ID on it. Restricting the rule to the port's service object keeps the rule working on a non-default port and stops the App-ID matching on other ports. Replace the placeholders with your own rule name and zones.

set service tcp-21 protocol tcp port 21

set rulebase security rules <rule-name> from <from-zone> to <to-zone> source any destination any application ftp service tcp-21 action allow

Risk and exposure

Rated high risk. Services on this port are commonly targeted by attackers. Keep it off the internet, or put it behind a VPN or a strict source allow-list, and monitor access.

Check it

• Linux ss -tlnp | grep :21
• PowerShell Test-NetConnection <host> -Port 21
• nmap nmap -p 21 <host>

Related ports

• 20 FTP Data
• 990 FTPS
• 23 Telnet
• 873 rsync

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