A company recently received a CDR bill. Upon analysis, the administrator sees a vast number of transfers to PSTN from incoming PSTN calls. How can this toll fraud scenario be remediated?

Setting the Cisco Unified Communications Manager (CUCM) Service Parameter 'Block Offnet to Offnet transfer' to true prevents calls that originate from the Public Switched Telephone Network (PSTN) from being transferred to another PSTN destination. This directly addresses the described toll fraud scenario by disallowing unauthorized forwarding of external calls back out to external numbers, effectively closing this common fraud vector.

The 'Use Restriction attribute of ID/Name Presentation of Transferring Party' relates to how caller ID information is presented during a transfer, not to blocking the transfer itself.

While gateways can have some controls, there isn't a direct 'block transfers' setting on a per-gateway basis in Cisco UCM specifically for off-net to off-net transfers; the service parameter is the intended global control.

A Toll fraud TCL script on the gateway could be used for custom fraud prevention, but it's not the primary or most direct mechanism within CUCM to block off-net to off-net transfers; the service parameter is a built-in feature for this specific scenario.