ABSTRACT
This chapter describes how the telephone system works, toll fraud, voice communications security concerns, and appli-cable techniques for any enterprise to protect its telecommunication infra-structure. However, this type of access should concern the security professional because the phone user will employ services such as calling cards and DISA to access the enterprise’s voice network. Because cellular and wireless access technologies are often subject to eavesdropping, the DISA access codes or calling card could potentially be retrieved from the wireless caller. If the DISA access number becomes known, an unauthorized user only needs to try random numbers to form an authorization code. Given enough time, they will eventually find one and start making what are free calls from their perspective. DISA allows a user to dial an access number, enter an authorization code, and appear to the PBX as an extension.
