Google Cloud Fraud Defense is a new system that uses device attestation to verify the legitimacy of devices accessing websites, which has raised concerns about privacy and the potential for Google to control access to the open web. The system is similar to a previously proposed mechanism called Web Environment Integrity, which was withdrawn due to objections from standards bodies. The new system uses a QR code challenge that requires a certified device to prove human presence. Critics argue that this system could be used to track users and exclude those who use non-certified devices or browsers.