1. Login as an administrator.
2. Enter into the editing mode.
3. Click the assign role icon in the header of the block to be hidden. (NOTE: Don't worry if you get an error message saying you are not able to assign role).
4. Scroll down to the settings block and click the "Permissions" link
5. In the View block section, click the X next to Guest.
6. Click the " Save changes" button.