Automatic threats require automatic solutions, which become automatic threats themselves. When software grows in functionality, it grows in complexity, and in the number of bugs. To keep track of and counter all of the possible ways that a malicious party can exploit these bugs, we need security software. Such software helps human developers identify and remove bugs, or system administrators detect attempted attacks. But like any other software, and likely more so, security software itself can have blind spots or flaws. In the best case, it stops working, and becomes ineffective. In the worst case, the security software has privileged access to the system it is supposed to protect, and the attacker can hijack those privileges for its own purposes. So we will need external programs to compensate for their weaknesses. At the same time, we need to minimize the additional attack surface and development time due to creating new solutions. To address both points, this thesis will explore how to combine multiple programs to overcome a number of weaknesses in individual security software: (1) When login authentication and physical protections of a smart phone fail, fake, decoy applications detect unauthorized usage and draw the attacker away from truly sensitive applications; (2) when a fuzzer, an automatic software testing tool, requires a diverse set of initial test inputs, manipulating the tools that a human uses to generate these inputs multiplies the generated inputs; (3) when the software responsible for detecting attacks, known as an intrusion detection system, itself needs protection against attacks, a simplified state machine tracks the software's interaction with the underlying platform, without the complexity and risks of a fully functional intrusion detection system; (4) when intrusion detection systems run on multiple, independent machines, a graph-theoretic framework drives the design for how the machines cooperatively monitor each other, forcing the attacker to not only perform more work, but also do so faster.
Instead of introducing new, stand-alone security software, the above solutions only require a fixed number of new tools that rely on a diverse selection of programs that already exist. Nor do any of the programs, old or new, require additional privileges that the old programs did not have before. In other words, we multiply the power of security software without multiplying their risks.
