This document summarizes the Stuxnet computer worm, which targeted industrial control systems. It provides a timeline of Stuxnet from 2008-2010, describes its infection mechanisms using zero-day exploits and stolen digital certificates. It explains how Stuxnet intercepted communications between Siemens Step 7 software and PLC controllers to reprogram industrial systems without detection. While the origins of Stuxnet are unknown, speculation points to the US, Israel, or other nation states as the likely creator in order to sabotage Iran's nuclear program.