Abstract Protecting commodity systems with commercial Operating Systems OSes) without significantly degrading performance or usability still remains an open problem. To make matters worse, the overall system security depends on desktop applications with complex code-bases that perform multiple and inter-dependent tasks often dictated by Internet-borne code. Recent research has shown the need for context-dependent trustworthy environments where the user can segregate different activities to lower risk of cross-contamination after an infection and safeguard private information. We introduce a novel BIOS-assisted mechanism to enable secure instantiation and management of trusted execution environments, tailored to separate security-sensitive activities from untrusted ones. A key characteristic of our system is usability: the capability to quickly and securely switch between operating environments in a single physical machine without requiring any specialized hardware or OS and application code modifications. Our goal is to eliminate any mutable, non-BIOS code sharing while securely reusing existing hardware. We demonstrate that, even if the untrusted OS becomes compromised, there is no potential for exfiltration or inference attack against data in the trusted OS. To safeguard against OS spoofing attacks, we can force the user to physically set a hardware switch, an action that cannot be reproduced by software. In addition, we provide visible indication to the user about the current environment leveraging one of the front panel Light Emitting Diodes (LEDs). Using our prototype implementation, we measured the switching process to be approximately six seconds on average. This quick and user-friendly switching process empowers the user to frequently and seamlessly alternate between trusted and untrusted environments. Speaker Bio Dr. Kun Sun is a Research Professor in the Center for Secure Information Systems (CSIS) at George Mason University. He received his Ph.D. in Computer Science from North Carolina State University in 2006. Before joining GMU, Dr. Sun was a Senior Research Scientist in Intelligent Automation Inc. From 2000 to 2001, Dr. Sun was a Member of the Technical Staff at Bell Labs, Lucent Technology. His current research focuses on trustworthy computing environment, moving target defense, enterprise-level security metrics, and security in MANET and wireless sensor networks.