Which technique could render a brute force biometric attack ineffective?

Using unique biometric samples each time can effectively render a brute force biometric attack ineffective because it introduces variability that complicates the attack process. In a brute force attack, an adversary attempts to gain access by trying every possible legitimate biometric measurement, such as fingerprints or iris scans, until finding a match. If the biometric verification system requires a different sample each time—such as a dynamic fingerprint pattern, an ever-changing voiceprint, or any biometric that changes over time—then the attacker cannot reliably replicate that sample.

This approach enhances security by ensuring that even if an attacker successfully obtains one biometric sample, they cannot use it repeatedly to gain continuous access, as future authentication will require a new, different sample. Therefore, the need for constant variation in biometric samples adds a layer of challenge for anyone attempting unauthorized access through brute force methods, significantly increasing the complexity and effort required for a successful attack.