Network Port: 20
Network Port Reference Guide
Registered Service Name
FTP Data Transfer
Transport Protocol
TCP
Functional Overview
Port 20 is utilized by the File Transfer Protocol (FTP) to transfer file data payloads between client and server hosts in Active Mode.
Security Risks & Vulnerabilities
FTP transmits data in cleartext. Sensitive files and data packets can be intercepted via packet sniffing. Modern deployments recommend SFTP (Port 22) or FTPS.
How to audit network port status
1. Scan Open Ports: Use our Port Scanner utility to verify if this port is actively listening on your host.
2. Verify Encryption: Audit the service layer to confirm SSL/TLS is protecting transmission payload.
3. Hardening Rules: Apply the firewall instructions below to shut down unauthorized inbound ports.
UFW Firewall Rules
Allow Command
sudo ufw allow 20/tcp
Block Command
sudo ufw deny 20/tcp
iptables Firewall Rules
Allow Command
sudo iptables -A INPUT -p tcp --dport 20 -j ACCEPT
Block Command
sudo iptables -A INPUT -p tcp --dport 20 -j DROP