Jan Schaumann is a Staff Information Security Engineer at Twitter. He has also worked in both small and large environments, including Etsy and Yahoo!. He holds a BS and MS in Computer Science from Stevens Institute of Technology.
Jan has been teaching the classes Advanced Programming in the UNIX Environment and Aspects of System Administration since 2004 and is currently working on a course book for teaching System Administration. He is involved in the NetBSD Project and in general a fan of scalable, secure open source software.
You can find (a little) more information on his course pages.