Digital is Calling the Analog: Robust Prevention of Dial Attacks

We carry out attacks using Internet platforms that aim on keeping telephone devices busy, denying users any access. We refer to this behavior using the term DIAL (Digital Initiated Abuse of teLephones), or, in the simple form, Dial attack. We develop an intuitive simulation environment for modeling a Dial attack in order to identify its critical characteristics. Based on the simulation’s results we perform the attack in the real world. By using a VoIP provider as the attack media, we manage to hold an existing landline device busy for 85% of the attack’s duration and thus render the device practically unusable. The attack has zero cost and requires negligible computational resources. Furthermore, as we show, anyone can practically launch a Dial attack towards any telephone device. However, in this paper, our primary goal is to protect telephones from Dial attacks. First, we investigate existing countermeasures in VoIP providers and show that they follow an all-or-nothing approach, but most importantly, their anomaly detection systems react slowly against our attacks. We managed to issue tens of thousands of calls before getting spotted. Second, using existing software technologies, Snort and Click, we present a flexible anomaly detection system, which promotes fairness to the callers. With our system in place it is hard for an adversary to keep the device busy for more than 5% of the attack’s duration.