An engineer is implementing toll fraud prevention for incoming calls cluster-wide on cisco UCM. What is the first step to configure this feature?

Setting 'Block OffNet to OffNet Transfer' to False would *disable* this crucial toll fraud prevention mechanism, leaving the system vulnerable.

Configuring blocking for inbound calls based on caller ID is a reactive measure for known fraudulent numbers and is not a comprehensive first step for cluster-wide toll fraud prevention.

'System Remote Access Blocked Numbers' is not a standard service parameter directly related to general toll fraud prevention for OffNet to OffNet transfers in CUCM.

The most fundamental and effective first step in preventing toll fraud, particularly for scenarios involving incoming calls being transferred to costly external destinations, is to set the 'Block OffNet To OffNet Transfer' service parameter to TRUE. This prevents external callers from being connected through the CUCM to other external numbers, which is a common vector for toll fraud.