Global ISR: Toward a Comprehensive Defense Against Unauthorized Code Execution

Abstract. Instruction-set randomization (ISR) obfuscates the “language” understood by a system to protect against code-injection attacks by pre-senting an ever-changing target. ISR was originally motivated by code in-jection through buffer overflow vulnerabilities. However, Stuxnet demon-strated that attackers can exploit other vectors to place malicious bina-ries into a victim’s filesystem and successfully launch them, bypassing most mechanisms proposed to counter buffer overflows. We propose the holistic adoption of ISR across the software stack, preventing the ex-ecution of unauthorized binaries and scripts regardless of their origin. Our approach requires that programs be randomized with different keys during a user-controlled installation, effectively combining the benefits of code whitelisting/signing and runtime program integrity. We discuss how an ISR-enabled environment for binaries can be implemented with little overhead in hardware, and show that higher-overhead software-only alternatives are possible. We use Perl and SQL to demonstrate the application of ISR in scripting environments with negligible overhead.