The lower levels of information classification in use by the US government are actually a grid, contrary to popular belief. Along one axis are:
- Unclassified
- Material with no sensitivity
- For Official Use Only (FOUO)
- Formerly Sensitive But Unclassified (SBU).
- Formerly Confidential.
- Used to denote information which should not be released to the public, but whose nature does not adversely affect national security. There are no codeword levels to FOUO.
- Secret (S)
- Information whose release could cause harm to national security.
- Top Secret (TS)
- Information whose release could cause grave harm to national security.
The second axis contains:
- Collateral
- A catchall for information classified at this level by its very nature.
- Sensitive Compartmented Information (SCI).
- Commonly referred to as "codeword". Information with an SCI designation will have a codeword designating the purpose of the classification. These codewords are classified at the same level (Secret/Top Secret), but Collateral.
- SCI codewords are usually buckets for different types of intelligence sources; information gathered via humint might fall into one bucket, whereas satellite imagery would fall into another. What Saddam Hussein eats for breakfast would likely be classified TS/SCI; the information has no intrinsic value; the fact that the US knows it reveals information about an intelligence source.
- There is secret and top secret data at the SCI level; it is not actually above those levels, but carries stricter requirements.
- Special Access Programs (SAP)
- This are programs which are only allowed to have a limited number of people aware of them at any one time. SAP members require third-party introductions to verify identity and clearance level. (A knows B, B knows C, A & C know of each other. For A&C to talk about a mutual SAP program requires an in-person introduction by B).
Given the shared nature of allied intelligence, much classified information will also designate a limitation on which countries can see the data. Typical subsets:
Things not covered here:
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