There is a possibility to disable access to the front of your site.

How to enable the offline page?
Step 1: Go to „System -> Global Configuration -> Site“.
Step 2: Click on „Yes“ for „Site Offline“ option.
Step 3: Fill in a text for „Offline Message“ to give your visitors some explanation about why your website is unavailable.
Step 4: Click on „Save“ to save your settings.

How to customize the offline page?
You need to edit the following file: /templates/jm-services/offline.php