Stephan is a security researcher at the Testlab mobile security group at the Fraunhofer Institute for Secure Information Technology (SIT). His main focus is Android application security testing and developing new static and dynamic analysis techniques for app security evaluation. He found different vulnerabilities in well-known Android applications and the AOSP. He gave talks on conferences like DEF CON, HITB, AppSec or VirusBulletin. In his spare time he enjoys teaching students in Android hacking.