Answer (C) is correct . Preventive controls are designed to prevent errors before they occur. Detective and corrective controls attempt to identify and correct errors. Preventive controls are usually more cost beneficial than detective or corrective controls. Allowing only authorized software from known sources to be used on the system is a preventive measure. The authorized software from known sources is expected to be free of viruses.
Answer (A) is incorrect because Comparing software with authorized versions is a detective control used to determine whether only authorized versions of the software are being used on the system.
Answer (B) is incorrect because Executing virus exterminator programs is a corrective control against a computer virus.
Answer (D) is incorrect because Preparing and testing a plan for virus recovery is a corrective control against a computer virus.
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