Which acts as a protective measure against unauthorized data access?

A firewall acts as a protective measure against unauthorized data access by monitoring and controlling incoming and outgoing network traffic based on predetermined security rules. Essentially, it serves as a barrier between a trusted internal network and an untrusted external network, such as the internet. By filtering out potentially harmful traffic and allowing only legitimate communication, firewalls help prevent unauthorized users from gaining access to sensitive data and systems.

In contrast, data redundancy involves storing multiple copies of data to ensure its availability in case of loss, but it doesn't intrinsically protect against unauthorized access. Public access refers to permissions that allow broad access to data, which can increase the risk of unauthorized access. Data transparency, while important for accountability and trust, does not serve to restrict access but rather makes information more accessible. Thus, the firewall is the most effective option in scenarios requiring protection from data breaches and unauthorized access.