From STEM to SEAD: Speculative Execution for Automated Defense

Most computer defense systems crash the process that they protect as part of their response to an attack. In contrast, self-healing software recovers from an attack by automatically repairing the underlying vulnerability. Although recent research explores the feasibility of the basic concept, self-healing faces four major obstacles before it can protect legacy applications and COTS software. Besides the practical issues involved in applying the system to such software (e.g., not modifying source code), self-healing has encountered a number of problems: knowing when to engage, knowing how to repair, and handling communication with external entities. Our previous work on a self-healing system, STEM, left these challenges as future work. STEM provides self-healing by speculatively executing “slices” of a process. This paper improves STEM’s capabilities along three lines: (1) applicability of the system to COTS software (STEM does not require source code, and it imposes a roughly 73% performance penalty on Apache’s normal operation), (2) semantic correctness of the repair (we introduce virtual proxies and repair policy to assist the healing process), and (3) creating a behavior profile based on aspects of data and control flow.