Whenever you change your password then for the verification, mail goes to your secondary email id to change the password, but if someone knows your password then he can change password of your Gmail account. For the security reason and avoid to suspicious login attempt of your account, you must make a setting in your Gmail account to send an SMS to your mobile phone. Whenever password will change by you or other than you then an SMS of verification code will be sent to your mobile phone to confirm the password change. If you had not changed the password and someone else tried to change your password then he cannot change password as he has to put the verification code which has sent on your mobile. So this way you can stop the suspicious login attempt of your email id.
Steps to Make Security of Your Gmail Account -:
1. Open Google Account Security Page
2. Select Checkbox of Password change and enter your mobile and verification code which has sent on your mobile as checked below.
So now your Google account is more secure than earlier. Enjoy the security settings.