Breaking into a computer consists, first of all, of discovering vulnerabilities and then creating an exploit (a program or set of instructions to be followed by hand) that takes advantage of the vulnerabilities. These vulnerabilities and their related exploit programs, if made public, are then used by many others, good and bad. For example, some users are system administrators using them to test their systems. Others are computer hackers just wanting to have fun. Then there are the crackers who scan systems to determine which computers have vulnerabilities and then carry out an attack, usually with a motive to get revenge or to make a profit off the attack. Crackers may even verify the success or failure of the attack - a form of personal delight.