Microsoft’s Trustworthy Computing initiative was 7 years old in 2009 when we first released the Enhanced Mitigation Experience Toolkit (EMET). Despite substantial improvements in Windows OS security during that same period, it was clear that the way we shipped Windows at the time (3-4 years between major releases) was simply too slow to respond quickly to emerging threats. Our commercial customers were particularly exposed since it often took years to deploy new OS versions in large scale environments. And thus, EMET was born as a stop-gap solution to deliver tactical mitigations against certain zero-day software vulnerabilities.
For Microsoft, EMET proved useful for a couple of reasons. First, it allowed us to interrupt and disrupt many of the common exploit kits employed by attackers at the time without waiting for the next Windows release, thus helping to protect our customers. Second, we were able to use EMET as a place to assess new features, which directly led to many security innovations in Windows 7, 8, 8.1, and 10.
But EMET has serious limits as well – precisely because it is not an integrated part of the operating system. First, many of EMET’s features were not developed as robust security solutions. As such, while they blocked techniques that exploits used in the past, they were not designed to offer real durable protection against exploits over time. Not surprisingly, one can find well-publicized, often trivial bypasses, readily available online to circumvent EMET.
Second, to accomplish its tasks, EMET hooks into low-level areas of the operating system in ways they weren’t originally designed. This has caused serious side-effects in both performance and reliability of the system and the applications running on it. And this presents an ongoing problem for customers since every OS or application update can trigger performance and reliability issues due to incompatibility with EMET.
Finally, while the OS has evolved beneath it, EMET hasn’t kept pace. While EMET 5.5x was verified to run on Windows 10, its effectiveness against modern exploit kits has not been demonstrated, especially in comparison to the many security innovations built-in to Windows 10.