The Criminal Use of Computer Systems
Unauthorised modification
Unauthorised modification means changing data, programs or settings on a computer system without permission. It is one of the three main offences under the Computer Misuse Act 1990, alongside unauthorised access and unauthorised access with the intention of committing another offence.
The change must be deliberate and made with no right to do it — a file that is damaged by accident is not this offence. For example, a pupil who edits the school's reward-points database to add 500 points to their own record has changed data without permission.
What counts as modification?
| Computer material | Authorised change | Unauthorised modification |
|---|---|---|
| Data | An office worker corrects a typing mistake in a customer's address | Someone edits the same customer's order to mark it as already paid |
| Program | A developer releases a bug fix | Someone alters the program so it skips a payment step |
| Settings | An administrator adds a new staff account | Someone gives themselves administrator rights without approval |
Installing malware counts as unauthorised modification, because it puts new files on a system and changes its settings without the owner's permission. Software can do the changing for you too: a free toolbar that switches a company's browser homepage and search engine to a different site has altered settings without permission, and a program that quietly creates extra user accounts has changed data.
Permission is the deciding factor. An IT technician updating a database as part of their job is authorised; someone making the same change without approval is committing an offence. Unauthorised modification can make records unreliable or stop software working, so the Computer Misuse Act 1990 sets a penalty of up to 10 years in prison and an unlimited fine.
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Pearson BTEC Digital Information Technology · The criminal use of computer systems