The recent raid on Mar-a-Lago has brought news stories about classified documents that Trump took from the White House when he left the presidency. That has led to people asking what are the classification levels in the U.S. government. Here’s the answer:
There are three basic levels of classification: confidential, secret, and top secret. The choice as to which level to use depends on whether an unauthorized disclosure of the information would result in damage, serious damage, or grave damage to national security.
Beyond that, there are a variety of additional classification subsets used to narrow access. They include but are not limited to codeword, compartmented, restricted access, NOFORN (no foreign distribution), and SCI (sensitive compartmented information). The codewords are themselves classified, but one, UMBRA, is well known publicly, thanks to security breaches by Edward Snowden, a cleared contractor, in 2013. It was in use during my time of working for the National Security Agency (NSA). Whether it is still used is not clear from the sources I consulted.
In short, our system for classifying information is intricate and well thought through. It works exceptionally well—very little classified information is compromised even though as of 2010, the most recent date for which I could find statistics, an estimated 854,000 people held top-secret security clearances.
Tom Glenn, Writer 