UK Cyber Law

Mon, 06 Jul 2026 00:00:00 +0000

The Computer Misuse Act 1990

The Computer Misuse Act 1990 (c. 18) is the primary legislation criminalising computer-related offences in the United Kingdom. Enacted following the Law Commission’s 1989 report on computer misuse and the influential decision in R v Gold and Schifreen (1988) 86 Cr App R 438 — in which the House of Lords overturned convictions for accessing a British Telecom voicemail system under the Forgery and Counterfeiting Act 1981 — the CMA establishes three principal offences: unauthorised access to computer material (section 1), unauthorised access with intent to commit or facilitate further offences (section 2), and unauthorised acts with intent to impair the operation of a computer (section 3). Section 3A, added by the Police and Justice Act 2006, criminalises the making, supplying, or obtaining of articles for use in computer misuse offences. The Act was substantially amended by the Serious Crime Act 2015, which introduced a new offence under section 3ZA of unauthorised acts causing serious damage, including damage to human welfare, the environment, the economy, or national security, with a maximum penalty of life imprisonment. The Act has extraterritorial application: section 4 provides jurisdiction where there is a significant link with the United Kingdom, including where the accused or the target computer is in the UK, or where the offence causes damage within the UK. The Crown Prosecution Service published revised guidelines on computer misuse prosecutions in 2023, emphasising the importance of these provisions in addressing state-sponsored cyber attacks and ransomware campaigns.

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UK Cyber Law

The Computer Misuse Act 1990