ftps

FTPS stands for File Transfer Protocol Secure and refers to a family of FTP extensions that add TLS (SSL) encryption to the traditional File Transfer Protocol. FTPS provides confidentiality and integrity for both the control channel, which carries commands, and the data channel, which carries file contents.

There are two main modes of FTPS. Explicit FTPS begins with a plain FTP connection on the standard port (typically 21) and then the client explicitly requests TLS by sending the AUTH TLS (or AUTH SSL) command. Once TLS negotiation succeeds, subsequent FTP commands and data transfers occur over the encrypted channel. Implicit FTPS starts TLS immediately as soon as the connection is made, typically on port 990, with the session remaining encrypted from the outset. After negotiation, the same FTP commands and data transfers occur over TLS.

FTPS relies on X.509 certificates for server authentication, and clients may optionally present certificates for client authentication. The security level of the data channel can be controlled after authentication using the PROT command, with PROT P indicating an encrypted data channel and PROT C indicating plaintext data.

FTPS is distinct from SFTP, which is a different protocol (SSH File Transfer Protocol) that runs over the SSH protocol rather than FTP over TLS. FTPS offers encryption while preserving FTP’s command set and semantics, but it can be more challenging to configure behind firewalls and NAT due to its use of additional encrypted and sometimes dynamically allocated data ports. Certificate management is another consideration for deployment.

FTPS is commonly used in enterprise environments that require encrypted file transfer and compatibility with existing FTP-based workflows.