Export Address Table Filtering (EMET v2)

I’ll tell you the truth: Export Address Table Filtering, the feature of the upcoming release of EMET, “designed to break nearly all shell code in use today”, intrigued me a bit.

Since I wasn’t able to find docs about the actual implementation, I started to think about how that could be done and I wrote a simple POC that uses VirtualProtect to flag the relevant pages of the .data section of ntdll and kernel32 with PAGE_GUARD to intercept read operations over the PEB.Ldr. A Vectored Exception Handler is then used to handle the exception and to check if the faulting address is within the code section of a module(MEMORY_BASIC_INFORMATION.Type == MEM_IMAGE). Here is the pseudo-code: