CAPTCHuring Automated (Smart) Phone Attacks

Abstract

Abstract-As the Internet has entered everyday life and become tightly bound to telephony, both in the form of Voice over IP technology as well as Internet-enabled cellular devices, several attacks have emerged that target both landline and mobile devices. We present a variation of an existing attack, that exploits smartphone devices to launch a DoS attack against a telephone device by issuing a large amount of missed calls. In that light, we conduct an excessive study of Phone CAPTCHA usage for preventing attacks that render telephone devices unusable, and provide information on the design and implementation of our system that protects landline devices. Subsequently, we propose the integration of Phone CAPTCHAs in smartphone software as a countermeasure against a series of attacks that target such devices. We also present various enhancements to strengthen CAPTCHAs against automated attacks. Finally, we conduct a user study to measure the applicability of our enhanced Phone CAPTCHAs.

On the viability of CAPTCHAs for use in telephony systems

“…We found Math-function captcha performed better than alphabet captcha, contrary to the existing work [11]. We found that alphabet captcha's accuracy was comparable to numeric captcha.…”