Common to hear to nowadays say on cases of hackers and/or crackers that they invade system of definitive company or companies to test the system or same to practise the calls vrituais crimes as robbery of passwords of banks among others. But come the question there Which the differences between Hacker and Cracker? It will be that all the robberies of bank passwords happen by means of the action of a Havker or Cracker? The reply of the first question it is that the difference between hacker and cracker and well simple hacker it even invades systems of companies in some cases for being contracted by these companies to test and to verify the vulnerability of the segunrana of the system. It is understood as system vulnerability: the Capacity of a system to be invaded by not authorized people that is the security of the system and to point possible imperfections of vulnerability of the system. Whereas cracker he uses knowledge the same technician of a Hacker to invade systems of companies to catch and to commercialize through a black market passwords and accounts you would bank and of orkut, social nets among others types of accounts of computadotr going until robbery of industrial secrets. There we have another question which the ethical limits of this activity? The ethical limits of this activity practically do not exist therefore of certain form the knowledge technician for these activities can be ultilizado in such a way to protect companies and customers of attacks of criminals as well as to invade companies and to practise the most varied crime. Everything depends and turns around one alone person who will go to ultilizar these conheciementos the behavior of this person and oque will define the ethical limits of this activity. For it saw generality to cracker ultiliza of programs of computers and nor does not send virus of computers for capture of password of users of computers generally who develops this the computer viruses professional are known as programmers who are contratatados by other people as: groups of people or same a person who can make possesss personal account a virus of same computer or to appeal to a programmer of computers to develop virus of computer and to vender these viruses for these people whom not necessarily they need to have some conhecimeneto computer technician to distribute virus of computers through diverse forms it saw Internet.