Former CIA Lawyer: Info with Potentially Lethal Consequences Passed Through Clinton Email

A former top lawyer to the CIA said Monday that potentially deadly intelligence information passed through Hillary Clinton's private email system.

John Rizzo, the former acting general counsel of the CIA, responded to news that Clinton confidante Sidney Blumenthal disclosed the name of a CIA source in an email to then-Secretary of State Clinton, who then forwarded that information to a colleague at the State Department.

"How dangerous is that [information] going over a public server that's held in someone's private home in Chappaqua, New York?" Morning Joe host Joe Scarborough said.

"It could be literally lethal," Rizzo said. "Who has access to that? Who is trying to hack into it? If this was a foreign-based source living in Libya, let's say, if you get outed as the CIA source over there, you're a dead man. So it couldn't be more serious."

Rizzo said that the names of human intelligence sources are some of the most sensitive information guarded by the CIA.

"That's the holiest of holies inside the CIA—the true identity of a secret source," Rizzo said. "Even inside CIA, in internal emails, in cables, you never mention or talk about the true name of a source. You use a pseudonym. So I mean, honestly, it's quite stunning."

Yahoo News investigative reporter Michael Isikoff said that this leak of classified information was "the single most problematic email exchange we've seen with Hillary Clinton yet."

Rizzo and Isikoff's assessments come one day after President Obama defended Clinton's private email use. Obama assured CBS that Clinton's email use did not endanger national security.

The FBI is carrying out a security review of Clinton's emails. If the CIA decides to press the matter, the latest leak could trigger a new investigation.

The Washington Free Beacon previously reported that this email exchange may constitute a violation of the Intelligence Identities Protection Act, meant to protect U.S. sources from reprisals.