Person:

Larochelle, David

Buffer overflow attacks may be today’s single most important security threat. This paper presents a new approach to mitigating buffer overflow vulnerabilities by detecting likely vulnerabilities through an analysis of the program source code. Our approach exploits information provided in semantic comments and uses lightweight and efficient static analyses. This paper describes an implementation of our approach that extends the LCLint annotation-assisted static checking tool. Our tool is as fast as a compiler and nearly as easy to use. We present experience using our approach to detect buffer overflow vulnerabilities in two security-sensitive programs.

Secure shell (SSH) can safely be called one of the rare successes in which a more secure technology has largely replaced a less secure but entrenched tool: telnet. We perform a market analysis to determine how and why SSH succeeded despite the existence of an entrenched legacy tool while similar technologies such as secure file transfer protocols have been far less successful. We show that network externalities, usually a first order effect, were not a significant factor impeding the adoption of SSH, and that SSH offered equivalent functionality and greater ease of use. We argue that these factors were the primary consideration in the willingness to change. Additionally, we argue that the openness of the standard, which facilitated the creation of numerous compatible implementations, was a key element in the economic decision made by system administrators.

We present a simple information security model to determine why, historically, the level of security has not increased despite numerous technical advances. In our model, the software design process involves trade-offs between security and functionality. Developers choose points in the design space corresponding to certain levels of security and functionality. If development resources, such as number of developers, time for completion, etc., are fixed, there is an implicit trade-off between security and functionality. We refer to the set of points that represent the maximum possible security given a certain level of functionality as the protection possibilities frontier (PPF). Technical advances push back the PPF expanding the set of accessible points in the design space potentially allowing both increased security and increased functionality. But historically this has not been sufficient to result in increased security. Instead almost all of the technical advancement is used to increase functionality. We examine how technical advances affect the marginal cost of security in terms of sacrificed functionality and classify technical advances into 3 categories: security neutral, security hostile, and security enhancing. In order for the level of security to increase, security enhancing technical advances must offset security hostile technical advances. We also observe that producing security enhancing technologies is surprisingly difficult. Even advances in information security technologies often result in the ability to take additional risks rather than increased security. Additionally we briefly examine user preferences, which to a large extant drive the actions of developers. We suggest that the lack of security cannot be explained purely by consumer apathy and that limited product availability and network externalities also contribute.