Port 21 (FTP)
File Transfer Protocol control channel. Data moves on a separate connection (port 20 or a negotiated port).
- Transport
- TCP
- Internet exposure
- Restrict
Expose only to specific networks, or behind a VPN.
Security notes
- Usernames, passwords and files travel in cleartext unless FTPS is used.
- Anonymous login left enabled is a common source of data exposure.
- Brute-force login attempts against FTP are routine internet background noise.
When it shows up in your logs
Inbound: scanning and password guessing. Outbound from a workstation: possible data exfiltration or malware download.
Related ports
- 20
- 22 SSH
- 990