War dialing is a process to dial any number with the use of a modem or a VOIP service in order to detect the terminal devices. In case of a modem, it automatically starts dialing a list of telephone numbers in order to search for computers, servers and fax machines, however, in case of VOIP a communication protocol IAX (Inter-Asterisk Exchange) is used for transmitting telephony session between a VOIP server and terminal device. It involves dialing any unknown telephone number, waiting for one or two rings and hanging up the connection once the phone to rings twice. Any modem or fax machine will answer the phone on the first ring and the hacker will make a note of that number. This facility can also be used to detect any unauthorized devices connected to a network which could possibly serve as an entry-point into the system.
WarVOX is an open source VOIP-based war dialing tool. It is used for exploring, classifying and auditing telephone systems. It analyses the pauses between words to identify numbers and classify telephone lines into modems, faxes, VOIP, PBXs, loop, IVRs, and forwarders. After installation warVOX can be accessed via http://localhost:7777. This presents a GUI interface allowing user to enter list of phone numbers to be dialed. Once the results of dialing are available warVOX allows the results to be analyzed. The analysis of results provide devices identified on the phone numbers.