Where do vulnerabilities come from?

Programming mistakes cause most vulnerabilities in software. A common mistake is failing to check the size of data buffers – a kind of storage bin of memory where a computer process executes its functions. When a buffer overflows, it overwrites data in adjacent memory buffers. This corrupts the stack or heap areas of memory, which may allow the execution of an attacker’s code on that machine via a virus, worm, or other unpleasant exploit.