Please make sure that your account password is secure; and that you have not shared a folder to other people with full-access right.
Most FTP client software can record FTP logs locally. DriveHQ FTP server doesn't attempt to log all FTP traffic as it will be too big. For better security, you can also use:
(1) FTP over SSL. Most FTP clients on Windows supports FTP over SSL. The data sent between client and server is encrypted.
(2) DriveHQ FileManager, which you can turn on SSL (HTTPS); you can even turn on "encrypted folder" and have your data encrypted on DriveHQ server.