About Alex Ionescu

Alex is coauthor of Windows Internals 5th edition.  He teaches Windows OS internals to Microsoft employees and other organizations worldwide. 

He is the founder of Winsider Seminars & Solutions Inc., specializing in low-level system software for administrators and developers. Alex was the lead kernel developer for ReactOS, an open source clone of Windows XP/2003 written from scratch, where he wrote most of the NT-based kernel.

Alex is also very active in the security research community, discovering and reporting several vulnerabilities related to the Windows kernel and presenting talks at conferences such as Blackhat and Recon.

Alex's experience in OS design and kernel coding dates back to his early adolescence when he first played with John Fine's educational OS, Kernel, and Boot Loader code. Since then, he has been active in the area of NT kernel development, offering help and advice for driver developers, as well as in the NT reverse engineering and security field, where he has published a number of articles and source code, such as documentation for the Linux NTFS project, extensive papers on the Visual Basic Metadata and Pseudo-code format, and NTFS Structures and Data Streams. In the last three years, he has also contributed to patches and development in two major commercially used operating system kernels.

For more information on Alex, see his web site and blog.