Final answer:
Parallel simulation is the auditing technique that processes actual or copied client data in a controlled environment to test the client's computer system controls.
Step-by-step explanation:
The computer assisted auditing technique that processes actual client input data (or a copy of the real data) on a controlled program under the auditor's control to periodically test controls in the client's computer system is known as Parallel simulation. This technique involves the auditor using audit software to replicate parts of the client's application system. The auditor then processes data using this replicated system to compare with the client's system for consistency and accuracy, thereby testing the controls within the client's system.