Building a portable deeply-nested implicit information flow tracking

Dynamic Information Flow Tracking has been successfully used to prevent a wide range of attacks and detect illegal access to sensitive information. Most proposed solutions only track the explicit information flow where the taint is propagated through data dependencies. However, recent evasion attacks exploit implicit flows, that use control flow in the application, to manipulate the data thus making the malicious activity undetectable. We propose NIFT - a nested implicit flow tracking mechanism that extends explicit propagation to instructions affected by a control dependency. Our technique generates taint instructions at compile time which are executed by specialized hardware to propagate taint implicitly even in cases of deeply-nested branches. In addition, we propose a restricted taint propagation for data executed in conditional branches that affects only immediate instructions instead of all instructions inside the branch scope. Our technique efficiently locates implicit flows and resolves them with negligible performance overhead. Moreover, it mitigates the over-tainting problem.