Some FTP clients send a series of random commands to maintain an unattended connection to an FTP Server. You may combat these commands by enabling Block anti-timeout schemes.
Start the Administrator Interface and connect to the Server.
At the bottom of the left pane, click the Server tab.
In the left pane, select the Site you want to modify.
In the right pane, click the Site Options tab.
Select the Block anti-timeout schemes check box.
Click Apply.
Blocking site-to-site transfers
Controlling access by IP address