Port 21: FTP
Open FTP port detected on a publicly accessible host.
Severity: Critical | Port: 21
What is FTP?
FTP (File Transfer Protocol) is one of the oldest protocols on the internet, designed in the 1970s for transferring files between computers. It works by establishing a connection on port 21 where a client can upload, download, and manage files on a remote server.
Why this is a problem
FTP transmits everything in plaintext — including usernames and passwords. Anyone monitoring network traffic between you and the server can read your credentials as they travel across the internet. Beyond the credential risk, FTP servers have a long history of security vulnerabilities and are a common target for automated attacks.
What you should do
- If FTP is not needed, disable the service and close port 21
- If file transfer is required, switch to SFTP (SSH File Transfer Protocol on port 22) or FTPS (FTP over TLS), which encrypt data in transit
- Restrict access to known IP addresses using firewall rules
- Ensure the FTP server software is up to date