Google has devised a way that allows its users to check if their Gmail Account has been hacked or accessed by someone else without their knowledge — in four simple steps.
Step 1: Go To My Account
Login to your Gmail account and click on the top right corner, where you can see either your picture or the first letter of your name. A pop-up will appear; select My Account.
Step 2: Go To Sign-in & security
On My Account page, select the Sign-in & Security option on the left side. Under the sub-options, select Device Activity & Security Events. When you scroll down the section, you will be greeted with information related to the devices that are or have used your Gmail Account. For example, if you are using your PC to login to your Gmail account to check your security status, it will label the device as Current Device.
Step 3: Inspect your recent activity
If you notice your account was used on an alien device or was accessed from an alien location, go to Recently used devices and click Review devices. There, you'll find a list of the devices that have been used to access your account in the last 28 days. If you see a device you don't recognize, you should remove it from your account immediately.
Step 4: Secure Your Account
If you feel that your account needs more protection, then on the Review devices page, click on the tab at the top of the page that direct you to Secure your account. From here you can go to Security checkup, change your password, add recovery information, and edit account permissions (used by applications such as WhatsApp and Google Chrome on your phone/web browse) to make sure no one gains access to your Gmail account. Through the Security checkup option, you can also create a password for applications that do not use 2-step verification.