Final answer:
The tellers' security procedure is a preventative control designed to secure the bank's cash from unauthorized access through unique codes and fingerprint scans.
Step-by-step explanation:
The unique code and fingerprint scan that bank tellers must use before accessing the bank's cash is a preventative control. This type of control is designed to prevent unauthorized access to the bank's funds, which could lead to theft or fraud. By requiring a unique code and a fingerprint scan, the bank is taking proactive steps to ensure that only authorized personnel can access the cash.