In this article I’m going to show you how you can secure cron.php file that is located in pub/cron.php. You may ask Why do I need to secure cron.php? The answer is: When you secure your cron.php, you have secured your Magento 2 store from the malicious exploit. If your cron is unsecured, any user can run Cron to attack your Magento application.
Read Complete Tutorial Here: http://www.cloudways.com/blog/how-to...php-magento-2/