How can I perform a high-level security assessment of my company's computing environment?

A. Microsoft has released the Microsoft Security Assessment Tool (MSAT), which you can download here. After extracting the content, execute the .msi file to install the assessment tool. I urge you to look at the user guide before using the tool.

The tool performs no system scanning. It's a series of 172 questions that ascertains technical and business processes and produces a report about security concerns that it deduces based on the information entered. Although administrators can use the tool directly, it's also designed to be run by Microsoft partners to help assess their clients' security status.