Computer Misuse Act

The Computer Misuse Act 1990 is UK legislation that protects computer systems, and the data stored on them, from unauthorised access and deliberate damage or disruption. It is a criminal law, so a person who breaks it can be taken to court.

Its purpose is to make it a criminal offence to access or change computer material — the programs and data held on a computer — without permission. The Act puts into writing what counts as misuse of a computer, so that the courts have a clear rule to apply instead of judging each case from scratch.

The Act provides the legal framework for deciding whether an action involving a computer is unlawful. It names the kinds of behaviour that are not allowed, such as accessing computer material without permission or causing deliberate damage to a computer or the service it provides. For example, a garden centre keeps its plant stock list on a computer. If someone outside the garden centre accesses that list without permission, the Act is what makes it a criminal offence. The same idea applies to any computer system and the data on it, whether it belongs to a business, a school or a public service.