Main Core is the code name of a database maintained since the 1980s by the federal government of the United States. Main Core contains personal and financial data of millions of U.S. citizens believed to be threats to national security. The data, which comes from the NSA, FBI, CIA, and other sources, is collected and stored without warrants or court orders. (…)

As of 2008 there were reportedly eight million Americans listed in the database as possible threats, often for trivial reasons, whom the government may choose to track, question, or detain in a time of crisis.
The existence of the database was first reported on in May 2008 by Christopher Ketcham and in July 2008 by Tim Shorrock.