Alex Ionescu is the founder of Winsider Seminars & Solutions Inc., specializing in low-level system software for administrators and developers as well as reverse engineering and security training for various organizations. He was a coauthor of the Windows Internals series for the last two editions. From 2003-2007, Alex was the lead kernel developer for ReactOS, an open source clone of Windows XP/Server 2003 written from scratch, for which he wrote most of the Windows NTbased kernel. During his studies in Computer Science, Alex worked at Apple on the iOS kernel, boot loader, firmware, and drivers on the original core platform team behind the iPhone, iPad, and AppleTV. Returning to his Windows security roots, Alex is now Chief Architect at CrowdStrike, a security start-up focused on nation-state adversaries and other highly sophisticated actors. Alex continues to be very active in the security research community, discovering and reporting several vulnerabilities related to the Windows kernel and presenting talks at conferences such as Black Hat, SyScan, and Recon. His work has frequently led to the discovery of a kernel vulnerabilities and design flaws, as well as to dozens of non-security bugs.