CompTIA Security+ Exam Prep

Answer: B - Wardialing allows attackers to dial large blocks of phone numbers in search of available modems. There are programs that allow for the calling of large blocks of phone numbers and take note of which were answered by a modem. Wardialers can be configured to call only those specific exchanges and their subset that are known to belong to a company. Often, numbers are dialed when phones are not monitored. Once a hacker knows what numbers have a modem, they can try to enter through the phone lines to obtain data.