Microsoft engineers have fortified the latest version of Windows with a feature designed to make it significantly harder for attackers to exploit bugs that may be lurking deep inside the operating system. The safeguard is called safe unlinking, and it's been dropped into a part of the Windows 7 kernel that allocates and deallocates chunks of memory. Safe unlinking performs a series of checks before entries are removed to make sure attackers aren't trying to exploit the operating system using what's known as a pool overrun. "This simple check blocks the most common exploit technique for pool overruns,"
More info: The Register