There are entire books dedicated to some of the tools out there for administrators and developers, which will prevent many exploits. They include items such as Data Execution Prevention (DEP), which would stop code like ours from working if the code and OS were configured to take advantage of it. This is done by preventing execution of data on the stack. We can bypass DEP by simply overwriting the Structured Exception Handling (SEH) to run our own code instead.

Stack Canaries, which are basically mathematical constructs in the stack, check when the return pointer is called. If the value has changed then something has gone wrong and an exception is raised. If an attacker determines the value the guard is checking for, it can be injected into the shellcode to prevent an exception.

Finally, there is Address Space Layer Randomization (ASLR), which randomizes locations in memory we take advantage of. ASLR is much tougher to beat than the other two, but it basically defeated by building your exploit in memory with components of shared libraries that have to maintain consistent memory locations. Without these consistent shared libraries, the OS would be unable to execute basic process initially. This technique is known as Return-Oriented Programming (ROP) chaining.