What is War dialing?

Understanding War dialing

The practice of using a computer program to scan telephone numbers and then later dial up a range of phone numbers to search for carriers computers modems and fax machines. War dialing is a reconnaissance technique that automatically calls large blocks of phone numbers to identify modems fax machines and other telecommunications systems that might provide unauthorized access to an organizations networks. While less common in modern environments due to the decline of dial-up connections the concept has evolved to scanning IP ranges voice over IP systems and wireless networks. War dialing is referenced in penetration testing methodologies and legacy telecom security standards. Organizations protect against war dialing through modem security policies telecom monitoring unauthorized connection detection and network access controls. For example despite modern connectivity a financial institution might still defend against war dialing attacks by maintaining an inventory of all authorized modems implementing callback verification for remote access disabling unused phone lines conducting regular audits for unauthorized modems and implementing anomaly detection to identify unusual calling patterns that might indicate war dialing reconnaissance. Related terms Wardriving Reconnaissance Phone phreaking Social engineering Unauthorized access Footprinting PBX security Modem security Telecom security Port scanning.