One of the most popular free and open-source FTP clients is FileZilla. In general, it's a pretty strong and secure FTP client program, based on its popularity and track record. It is not regarded as secure.  FTP, FTPS (FTP over SSL/TLS), and SFTP are all supported by FileZilla (SSH FTP). Both FTPS and SFTP are extremely safe (with data encryption). Filezilla is a cross-platform file-sharing server that has been rated untrustworthy.