LIBRARIES

We present program shepherding, a method for monitoring control flow transfers dur-ing program execution in order to enforce a security policy. Program shepherding provides three basic techniques as building blocks for security policies. First, pro-gram shepherding can restrict execution privileges on the basis of code origins. This distinction can ensure that malicious code masquerading as data is never executed, thwarting a large class of security attacks. Second, shepherding can restrict control transfers based on instruction type, source, and target. Finally, shepherding guaran-tees that sandboxing checks around any program operation will never be bypassed. Security attacks use inevitable bugs in trusted binaries to coerce a program into performing actions that it was never intended to perform. We use static and dynamic analyses to automatically build a custom security policy for a target program, which specifies the program's execution model. An accurate execution model restricts control flow transfers only to the intended ones and can thwart attacker attempts to alter program execution. For example, shepherding will allow execution of shared librar