Details can be found in this informative research report issued by Microsoft security:
QUOTE: In our previous posts in this series, we described various mitigation improvements that attempt to prevent the exploitation of specific classes of memory safety vulnerabilities such as those that involve stack corruption, heap corruption, and unsafe list management and reference count mismanagement. These mitigations are typically associated with a specific developer mistake such as writing beyond the bounds of a stack or heap buffer, failing to correctly track reference counts, and so on. As a result, these mitigations generally attempt to detect side-effects of such mistakes before an attacker can get further along in the exploitation process, e.g. before they gain control of the instruction pointer.
Another approach to mitigating exploitation is to focus on breaking techniques that can apply to many different classes of memory safety vulnerabilities. These mitigations can have a broader impact because they apply to techniques that are used further along in the process of exploiting many vulnerabilities. For example, once an attacker has gained control of the instruction pointer through an arbitrary vulnerability, they will inherently need to know the address of useful executable code to set it to. This is where well-known mitigations like Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) come into play – both of which have been supported on Windows for many releases now. When combined, these mitigations have proven that they can make it very difficult to exploit many classes of memory safety vulnerabilities even when an attacker has gained control of the instruction pointer.