Leakage of restricted government information can impair state security, hinder development and weaken government policies, whether it is leaked to a foreign power, to the public via the press or other media, or to private business interests. Leakage may arise out of inefficient security measures or from complicity of those with a legitimate access. Journalists are often "leaked" documents to ensure timely coverage in the press. A leakage of official secrets to a foreign power may go undiscovered for a comparatively long time if complicity is involved and if knowledge of the information is not sufficiently distributed for supervision to be effective. Leakage of industrial secrets can affect whole populations in several countries for generations.
Following the change of regimes in eastern Europe, the files of the communist secret service were gradually released or sold. This has provided material for attacks on individuals, often with little regard for the truth. The contents of such files can often be misconstrued to brand people as informers and collaborators. Investigations have shown that allegations were often unfounded. Such files can easily be contaminated with misleading entries and erasures by superiors trying to disguise the truth, or simply by lies on the part of agents seeking recognition.
There are more than 100 UK laws that make disclosure of information a crime under the amended Secrets Act.