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2020-04-20
Lecuyer, Mathias, Atlidakis, Vaggelis, Geambasu, Roxana, Hsu, Daniel, Jana, Suman.  2019.  Certified Robustness to Adversarial Examples with Differential Privacy. 2019 IEEE Symposium on Security and Privacy (SP). :656–672.
Adversarial examples that fool machine learning models, particularly deep neural networks, have been a topic of intense research interest, with attacks and defenses being developed in a tight back-and-forth. Most past defenses are best effort and have been shown to be vulnerable to sophisticated attacks. Recently a set of certified defenses have been introduced, which provide guarantees of robustness to norm-bounded attacks. However these defenses either do not scale to large datasets or are limited in the types of models they can support. This paper presents the first certified defense that both scales to large networks and datasets (such as Google's Inception network for ImageNet) and applies broadly to arbitrary model types. Our defense, called PixelDP, is based on a novel connection between robustness against adversarial examples and differential privacy, a cryptographically-inspired privacy formalism, that provides a rigorous, generic, and flexible foundation for defense.
2018-05-02
Petsios, Theofilos, Zhao, Jason, Keromytis, Angelos D., Jana, Suman.  2017.  SlowFuzz: Automated Domain-Independent Detection of Algorithmic Complexity Vulnerabilities. Proceedings of the 2017 ACM SIGSAC Conference on Computer and Communications Security. :2155–2168.
Algorithmic complexity vulnerabilities occur when the worst-case time/space complexity of an application is significantly higher than the respective average case for particular user-controlled inputs. When such conditions are met, an attacker can launch Denial-of-Service attacks against a vulnerable application by providing inputs that trigger the worst-case behavior. Such attacks have been known to have serious effects on production systems, take down entire websites, or lead to bypasses of Web Application Firewalls. Unfortunately, existing detection mechanisms for algorithmic complexity vulnerabilities are domain-specific and often require significant manual effort. In this paper, we design, implement, and evaluate SlowFuzz, a domain-independent framework for automatically finding algorithmic complexity vulnerabilities. SlowFuzz automatically finds inputs that trigger worst-case algorithmic behavior in the tested binary. SlowFuzz uses resource-usage-guided evolutionary search techniques to automatically find inputs that maximize computational resource utilization for a given application. We demonstrate that SlowFuzz successfully generates inputs that match the theoretical worst-case performance for several well-known algorithms. SlowFuzz was also able to generate a large number of inputs that trigger different algorithmic complexity vulnerabilities in real-world applications, including various zip parsers used in antivirus software, regular expression libraries used in Web Application Firewalls, as well as hash table implementations used in Web applications. In particular, SlowFuzz generated inputs that achieve 300-times slowdown in the decompression routine of the bzip utility, discovered regular expressions that exhibit matching times exponential in the input size, and also managed to automatically produce inputs that trigger a high number of collisions in PHP's default hashtable implementation.
2017-03-27
Argyros, George, Stais, Ioannis, Jana, Suman, Keromytis, Angelos D., Kiayias, Aggelos.  2016.  SFADiff: Automated Evasion Attacks and Fingerprinting Using Black-box Differential Automata Learning. Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security. :1690–1701.

Finding differences between programs with similar functionality is an important security problem as such differences can be used for fingerprinting or creating evasion attacks against security software like Web Application Firewalls (WAFs) which are designed to detect malicious inputs to web applications. In this paper, we present SFADIFF, a black-box differential testing framework based on Symbolic Finite Automata (SFA) learning. SFADIFF can automatically find differences between a set of programs with comparable functionality. Unlike existing differential testing techniques, instead of searching for each difference individually, SFADIFF infers SFA models of the target programs using black-box queries and systematically enumerates the differences between the inferred SFA models. All differences between the inferred models are checked against the corresponding programs. Any difference between the models, that does not result in a difference between the corresponding programs, is used as a counterexample for further refinement of the inferred models. SFADIFF's model-based approach, unlike existing differential testing tools, also support fully automated root cause analysis in a domain-independent manner. We evaluate SFADIFF in three different settings for finding discrepancies between: (i) three TCP implementations, (ii) four WAFs, and (iii) HTML/JavaScript parsing implementations in WAFs and web browsers. Our results demonstrate that SFADIFF is able to identify and enumerate the differences systematically and efficiently in all these settings. We show that SFADIFF is able to find differences not only between different WAFs but also between different versions of the same WAF. SFADIFF is also able to discover three previously-unknown differences between the HTML/JavaScript parsers of two popular WAFs (PHPIDS 0.7 and Expose 2.4.0) and the corresponding parsers of Google Chrome, Firefox, Safari, and Internet Explorer. We confirm that all these differences can be used to evade the WAFs and launch successful cross-site scripting attacks.