In the government, defense and intelligence (GDI) arena, the practice of assigning different levels of security classification to information (whether written notes, printed reports or data held in information systems) based on its sensitivity is very familiar. The levels of classification dictate how the information is shared, stored and accessed.
In the GDI arena, it is common practice to limit access to such material based on the level of security clearance held by an individual. The specifics of security clearances are discussed in the appendices, however one common thread is that, regardless of the nature and sensitivity of the information, it should be made available only to those who have a need to know. The concept of 'need to know' is more critical to the protection of information than anything else.
In the UK public sector, material that carries an official classification is referred to as being 'protectively marked'; in the United States, it's simply referred to as 'classified'. Both governments, though their security clearance procedures are very different, use broadly the same categories of data classification. They are discussed in the following sections, from low to high classification.
This is not a classification per se, but a formal declaration that the content may be viewed by staff without a security clearance, assuming of course they have the requisite need to know. Sometimes ...