An administrator needs to prevent toll fraud on Cisco unity connection. Which action should be taken to accomplish this task?

The Class of Restriction (COR) in Cisco Unity Connection is the built-in mechanism designed specifically to restrict call types (such as long-distance or international) that voicemail users can trigger via transfers or delivery rules. Modifying the COR tables directly on Unity Connection is the correct and supported method to block toll fraud originating from the voicemail system.

COR on a Cisco IOS Voice Gateway controls call routing at the gateway level, not within Unity Connection itself, so it does not address toll fraud initiated by the voicemail system.

Restricting calls to the operator is only one narrow category; setting all restriction tables to block the operator does not comprehensively prevent toll fraud to long-distance or international numbers.

Assigning a Calling Search Space (CSS) without calling rights applies to CUCM directory numbers, not to Unity Connection, so it does not control what calls Unity Connection can place.