Which of the following is not a common firmware defense mechanism for protecting against exploits?

Using open-source firmware is not traditionally considered a common defense mechanism for protecting against firmware exploits. While open-source firmware has its own merits, such as transparency and community-driven development, it does not inherently include specific security features designed to protect against exploits. Security mechanisms are more focused on methods like encrypting firmware, implementing regular updates, and utilizing hardware authentication to safeguard firmware from unauthorized modifications and attacks.

Encrypting firmware helps in preventing tampering and ensures that only authenticated code can be executed. Regular updates enable the deployment of security patches and improvements that can address newly discovered vulnerabilities. Hardware authentication is a crucial mechanism to verify the integrity of firmware and ensure that only trusted firmware can run on the hardware, thereby thwarting potential exploits. In contrast, using open-source firmware doesn't automatically provide these specific protections, which is why it stands out as an option that does not align with common firmware defense strategies.