System Cracking , the defeating of security devices in computer networks, the process of gaining unauthorized access to a computer system (typically carried out by a Black-hat Hacker ). Cracking can be defined as the act of entering a Computer or Computer Network by force, whereas Hacking does so by manipulation.
The value difference between a Crude Oil & oil products (usually per Barrel ) or different oil products, for instance a mogas crack - the difference between mogas & crude oil.