Port 20 · FTP Data

Port 20 is FTP Data, TCP.

FTP active mode data transfer channel. Unencrypted — credentials and data in cleartext.

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-20 protocol tcp port 20

set rulebase security rules <rule-name> from <from-zone> to <to-zone> source any destination any application ftp service tcp-20 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 :20
• PowerShell Test-NetConnection <host> -Port 20
• nmap nmap -p 20 <host>

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• 21 FTP Control
• 990 FTPS
• 23 Telnet
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