Design-Level and Code-Level Security Analysis of IoT Devices

The Internet of Things (IoT) is playing an important role in different aspects of our lives. Smart grids, smart cars, and medical devices all incorporate IoT devices as key components. The ubiquity and criticality of these devices make them an attractive target for attackers. Therefore, we need techniques to analyze their security so that we can address their potential vulnerabilities. IoT devices, unlike remote servers, are user-facing and, therefore, an attacker may interact with them more extensively, e.g., via physical access. Existing techniques for analyzing security of IoT devices either rely on a pre-defined set of attacks and, therefore, have limited effect or do not consider the specific capabilities the attackers have against IoT devices. Security analysis techniques may operate at the design-level, leveraging abstraction to avoid state-space explosion, or at the code-level for ensuring accuracy. In this article, we introduce two techniques, one at the design-level, and the other at the code-level, to analyze security of IoT devices, and compare their effectiveness. The former technique uses model checking, while the latter uses symbolic execution, to find attacks based on the attacker's capabilities. We evaluate our techniques on an open source smart meter. We find that our code-level analysis technique is able to find three times more attacks and complete the analysis in half the time, compared to the design-level analysis technique, with no false positives.