Thanks for reaching out. For an added layer of security, I recommend enabling two-step verification on your account. Whenever you sign in, you’ll need to enter a temporary, unique code that’s sent to your phone. In that way, only you can access your account and without the code whoever tries to access your account wouldn’t be able to. Have a look at this article: Manage your Nest app account security and emails.
Let me know if there’s anything else.