4 : Check Suspicious Activity
If Google notices suspicious activity in your account they’ll send you a notification.
It may be that there are sign-ins from an unfamiliar location or an unfamiliar device. Ideally you should also manually review your account at least once a month to make sure that no suspicious activity has taken place.
To review your account, click on the link ‘Details’ located on the right hand side of the footer of your mailbox.