Windows Update Can Hurt Security

An anonymous reader writes "Researchers at Carnegie Mellon University have shown that given a buggy program with an unknown vulnerability, and a patch, it is possible automatically to create an exploit for unpatched systems. They demonstrate this by showing automatic patch-based exploit generation for several Windows vulnerabilities and patches can be achieved within a few minutes of when a patch is first released. From the article: 'One important security implication is that current patch distribution schemes which stagger patch distribution over long time periods, such as Windows Update... can detract from overall security, and should be redesigned.' The full paper is available as PDF, and will appear at the IEEE Security and Privacy Symposium in May."

Comments

Automatically deriving exploits by theorem proving

[Animats]

This is fascinating. As someone who's worked with automatic theorem proving and proof of correctness techniques, I'd never thought of using them in this way.

What they're doing works like a proof of correctness system in reverse. They difference executables before and after the patch (which in itself is impressive), then, having isolated the patch, analyze it automatically. Security patches usually consist of adding a test which constrains the valid inputs at some point. So they use a symbolic decision procedure, which is part of a theorem prover, to work back through the code and automatically derive a set of inputs that would be caught by the new test.

This is more than just an attack on Windows Update. It's true automated exploit generation.

This is potentially applicable to any security-critical code that changes over time. One could, for example, have something that watched check-ins to the Linux kernel tree and developed new exploits to current stable releases from them.