Final answer:
User Account Control (UAC) is the Windows security component responsible for controlling user access to Windows resources, by prompting for administrative credentials or confirmation before making changes that require elevated permissions.
Step-by-step explanation:
The Windows security component responsible for controlling access of a user to Windows resources is User Account Control (UAC). User Account Control is a security feature that helps prevent unauthorized changes to the operating system. When a software or a user attempts to make a change that requires administrator-level permission, UAC issues a prompt requesting administrative credentials or confirmation. This helps to safeguard the system by ensuring that changes are made with the user's knowledge and consent. Other options such as firewall, antivirus software, and Windows Defender provide additional security measures such as protecting against external threats, scanning for malware, and removing security threats, but they do not specifically control user access to resources.