Formal Specification and Verification of a Selective Defense for TDoS Attacks

Telephony Denial of Service (TDoS) attacks target telephony services, such as Voice over IP, not allowing legitimate users to make calls. There are few defenses that attempt to mitigate TDoS attacks, most of them using IP filtering, with limited applicability. In our recent work, we proposed to use selective strategies for mitigating HTTP Application-Layer DDoS Attacks demonstrating their effectiveness in mitigating different types of attacks. This paper demonstrates that selective strategies can also be successfully used to mitigate TDoS attacks, in particular, two attacks: the Coordinated Call Attack and the Prank Call attack. We formalize a novel selective strategy for mitigating these attacks in the computational tool Maude and verify these defenses using the statistical model checker PVeStA. When compared to our experimental results (reported elsewhere), the results obtained by using formal methods were very similar. This demonstrate that formal methods is a powerful tool for specifying defenses for mitigating Distributed Denial of Service attacks allowing to increase our confidence on the proposed defense before actual implementation.