In a medium$-$sized tech company, employees have different roles and responsibilities requiring access to specific resources and data. The IT team is implementing security measures to control access effectively and reduce the risk of unauthorized activities. What security measure could the IT team implement in the tech company to control access effectively and minimize the risk of unauthorized activities?

A$.$ Implement intrusion detection systems to monitor and identify potential security breaches

B$.$ Implement a firewall to protect the company's network from external threats

C$.$ Enforce mandatory password changes every month to enhance password security

D$.$ The principle of least privilege to grant employees the minimum needed access based on job roles