Biblio

Despite decades of research on software diversification, only address space layout randomization has seen widespread adoption. Code randomization, an effective defense against return-oriented programming exploits, has remained an academic exercise mainly due to i) the lack of a transparent and streamlined deployment model that does not disrupt existing software distribution norms, and ii) the inherent incompatibility of program variants with error reporting, whitelisting, patching, and other operations that rely on code uniformity. In this work we present compiler-assisted code randomization (CCR), a hybrid approach that relies on compiler-rewriter cooperation to enable fast and robust fine-grained code randomization on end-user systems, while maintaining compatibility with existing software distribution models. The main concept behind CCR is to augment binaries with a minimal set of transformation-assisting metadata, which i) facilitate rapid fine-grained code transformation at installation or load time, and ii) form the basis for reversing any applied code transformation when needed, to maintain compatibility with existing mechanisms that rely on referencing the original code. We have implemented a prototype of this approach by extending the LLVM compiler toolchain, and developing a simple binary rewriter that leverages the embedded metadata to generate randomized variants using basic block reordering. The results of our experimental evaluation demonstrate the feasibility and practicality of CCR, as on average it incurs a modest file size increase of 11.46% and a negligible runtime overhead of 0.28%, while it is compatible with link-time optimization and control flow integrity.

Malware sandboxes, widely used by antivirus companies, mobile application marketplaces, threat detection appliances, and security researchers, face the challenge of environment-aware malware that alters its behavior once it detects that it is being executed on an analysis environment. Recent efforts attempt to deal with this problem mostly by ensuring that well-known properties of analysis environments are replaced with realistic values, and that any instrumentation artifacts remain hidden. For sandboxes implemented using virtual machines, this can be achieved by scrubbing vendor-specific drivers, processes, BIOS versions, and other VM-revealing indicators, while more sophisticated sandboxes move away from emulation-based and virtualization-based systems towards bare-metal hosts. We observe that as the fidelity and transparency of dynamic malware analysis systems improves, malware authors can resort to other system characteristics that are indicative of artificial environments. We present a novel class of sandbox evasion techniques that exploit the "wear and tear" that inevitably occurs on real systems as a result of normal use. By moving beyond how realistic a system looks like, to how realistic its past use looks like, malware can effectively evade even sandboxes that do not expose any instrumentation indicators, including bare-metal systems. We investigate the feasibility of this evasion strategy by conducting a large-scale study of wear-and-tear artifacts collected from real user devices and publicly available malware analysis services. The results of our evaluation are alarming: using simple decision trees derived from the analyzed data, malware can determine that a system is an artificial environment and not a real user device with an accuracy of 92.86%. As a step towards defending against wear-and-tear malware evasion, we develop statistical models that capture a system's age and degree of use, which can be used to aid sandbox operators in creating system i- ages that exhibit a realistic wear-and-tear state.

The continuous discovery of exploitable vulnerabilitiesin popular applications (e.g., web browsers and documentviewers), along with their heightening protections against control flow hijacking, has opened the door to an oftenneglected attack strategy-namely, data-only attacks. In thispaper, we demonstrate the practicality of the threat posedby data-only attacks that harness the power of memorydisclosure vulnerabilities. To do so, we introduce memorycartography, a technique that simplifies the construction ofdata-only attacks in a reliable manner. Specifically, we showhow an adversary can use a provided memory mapping primitive to navigate through process memory at runtime, andsafely reach security-critical data that can then be modifiedat will. We demonstrate this capability by using our cross-platform memory cartography framework implementation toconstruct data-only exploits against Internet Explorer and Chrome. The outcome of these exploits ranges from simple HTTP cookie leakage, to the alteration of the same originpolicy for targeted domains, which enables the cross-originexecution of arbitrary script code. The ease with which we can undermine the security ofmodern browsers stems from the fact that although isolationpolicies (such as the same origin policy) are enforced atthe script level, these policies are not well reflected in theunderlying sandbox process models used for compartmentalization. This gap exists because the complex demands oftoday's web functionality make the goal of enforcing thesame origin policy through process isolation a difficult oneto realize in practice, especially when backward compatibility is a priority (e.g., for support of cross-origin IFRAMEs). While fixing the underlying problems likely requires a majorrefactoring of the security architecture of modern browsers(in the long term), we explore several defenses, includingglobal variable randomization, that can limit the power ofthe attacks presented herein.