[Ed. – This is, indeed, some of our most exceptionally sensitive national intelligence. Exposing the existence of it puts live directly at risk.]
At least one of the emails on Hillary Clinton’s private server contained extremely sensitive information identified by an intelligence agency as “HCS-O,” which is the code used for reporting on human intelligence sources in ongoing operations, according to two sources not authorized to speak on the record.
Both sources are familiar with the intelligence community inspector general’s January 14 letter to Congress, advising the Oversight committees that intelligence beyond Top Secret — known as Special Access Program (SAP) — was identified in the Clinton emails, as well the supporting documents from the affected agencies that owned the information and have final say on classification.
According to a December 2013 policy document released by the Office of the Director of National Intelligence: This designation “is used to protect exceptionally fragile and unique IC (intelligence community) clandestine HUMINT operations and methods that are not intended for dissemination outside of the originating agency.” …
Separately, Fox News has learned that the so-called “spillage” of classified information is greater than the “several dozen” emails identified in the January 14 letter to Congress, which also acknowledged for the first time, that the Clinton emails contained intelligence beyond Top Secret, also known as Special Access Programs (SAPs).