Nest has finally launched two-factor authentication to prevent hackers from accessing your camera feeds or any other personal info. You can activate the feature under Account Security in the Nest app. If you do, you'll start getting a verification code through text every time you log into your account. Just take note that you'll get booted out and will need to sign in again right after you switch the feature on.
Back in early 2016, Princeton researchers discovered that Nest thermostats leaked customer zip codes on the internet, though the company quickly patched the flaw. Other security researchers also showed that attackers could use Nest as an entry point to gain control of your home. Text-based two-factor authentication isn't exactly the best or the most secure option, since the most persistent attackers could hijack your SMS. However, it still adds an extra layer of protection on top of your (hopefully strong) password.