Computer hacking is done by hackers who get involved in the computer security or insecurity by specializing in the discovery of exploits in system [ for exploitation or prevention ] or in obtaining or preventing unauthorized access to systems through tactics, skills and detailed knowledge. Those individuals who involve in the hacking activity are referring to the cyber-criminals. Hacking is an illegal activity even in credit cards and other frauds, that which can put person behind bars. Hackers also commonly use port scanners to gain unauthorized gain into others systems. Hacking requires a through knowledge of different computer systems and the individual has to know entire workings and sub workings in the computer. Hacking can be both positive and negative and it entirely depends on the nature of working.