Congress has provided special protection in the FOIA for three narrow categories of law enforcement and national security records. The provisions protecting those records are known as “exclusions.” The first exclusion protects the existence of an ongoing criminal law enforcement investigation when the subject of the investigation is unaware that it is pending and disclosure could reasonably be expected to interfere with enforcement proceedings.  The second exclusion is limited to criminal law enforcement agencies and protects the existence of informant records when the informant’s status has not been officially confirmed.  The third exclusion is limited to the Federal Bureau of Investigation and protects the existence of foreign intelligence or counterintelligence, or international terrorism records when the existence of such records is classified.  Records falling within an exclusion are not subject to the requirements of the FOIA.  So, when an office or agency responds to your request, its response will encompass those records that are subject to the FOIA.