From the doc: '1. Open the exe-file on the computer you wanna connect to. 2. Connect to the host with an FTP-client on port 90000. Secret commands: If you create a directory with the name 'removeftp' in c:, the FTP Backdoor and all it's traces will be erased from the victim and the backdoor will shutdown. The directory you have created will be deleted too. If you create a directory with the name 'closeftp' in c:, the FTP Backddor will be closed but it will be started after a reboot. The directory you have created will be deleted too.'
ftp backdoor.exe