Described systems and methods allow protecting a host system against malware, using hardware virtualization technology. A memory introspection engine executes at the level of a hypervisor, protecting a virtual machine (VM) from exploits targeting the call stack of a thread executing within the respective VM. The introspection engine identifies a virtual memory page reserved for the stack, but not committed to the stack, and intercepts an attempt to write to the respective page. In response to intercepting the write attempt, the memory introspection engine marks the respective page as non-executable, thus protecting the stack against exploits.