hacking the accessing of a computer system without the permission of the owner of that system. Originally the practice proved difficult for the legal system mainly because many hackers caused no actual damage - they would simply enter the system, leave proof of their cunning and skill and exit. Others, however, were more malicious. Offences have been created to protect the integrity of systems, initially in computer misuse legislation from 1980. A person is guilty of an offence if he causes a computer to perform any function with intent to secure access to any program or data held in any computer; the access he intends to secure is unauthorized; and he knows at the time when he causes the computer to perform the function that this is the case. There is a related offence of unauthorized modification, namely to do any act which causes an unauthorized modification of the contents of any computer; and at the time the accused does the act, he has the requisite intent and the requisite knowledge. The intent required is intent to impair the operation of any computer, prevent or hinder access to any program or data held on any computer, or impair the operation of any program or the reliability of any data. It is immaterial whether or not the accused had any intent directed towards any particular computer system, program or data; all that is required is that the accused knows that any intended alteration is unauthorized.