It takes just a couple of minutes and, unlike other checkups, it won’t leave you feeling guilty about not flossing. Here’s what it does:
- Ensures your account recovery information is current
If we detect suspicious activity in your account, we use your recovery info to get in touch and make sure no one but you gains access. - Lets you review recent sign-in activity
Reviewing this lets you validate the sign-ins are coming from you and not someone who shouldn't be using your credentials. - Confirms the apps and devices that access some account information
This step lets you monitor this list and remove apps and devices that don't need access to your account any more.
After you’ve gone through the checkup successfully, you’ll see three green checkboxes (see below) that confirm you’re eligible for the free storage and, more importantly, that you’ve taken steps to enhance your online safety. We’ll be granting the storage automatically to everyone around 28 February 2015 and we’ll send you an email when your adjustment is complete.

UPDATE: Google Apps for Work and Google Apps for Education users are not eligible for the bonus storage but should still consider taking the Security Checkup.
Posted by Alex Vogenthaler, Group Product Manager, Google Drive