Data security is a top priority for the census. In addition to the strong protection provided by the law, ONS has put in place stringent additional safeguards.


All staff who have access to the full census data set work for ONS. All staff processing census data are security cleared. This requirement has also been extended to all employees of the supplier and their sub-contractors handling any personal census data.

Staff with access to the full census data set or substantial parts of it will have security clearance to handle material classified as ‘Secret’.

Standards and guidelines

Underlying security requirements for census data are based upon UK Government security guidelines issued by the Cabinet Office and by GCHQ’s Communications-Electronic Security Group (CESG) which provides assistance to government departments on their own communications security.

The census security programme is managed to the framework of ISO27001 - the internationally recognised Information Security Management Standard.

Security classification

Census data are classified as restricted under the Security Policy Framework, the scheme of classification of government information. This classification brings a whole set of standards and safeguards which have been put in place to ensure that the data remain secure. This includes control of physical access to any site or room where the data are kept, secure control of access to IT hardware and of course IT systems.


ONS controls system access rights to all systems and data.

All security measures cover the completed questionnaires, the electronic data set, the website, the archive image system and the communications links relating to any of these items.

All of the electronic communications links used for routing personal census information are encrypted (scrambled) to the levels recommended by the Government Security Services.


For more information about the classification scheme for government information, see the Security Policy Framework on the Cabinet Office website.