Secretary of State Hillary Clinton received no security briefings on the proper handling of classified materials in three of her four years at the State Department, according to documents released by department officials to The Daily Caller News Foundation under a Freedom of Information request.

Clinton’s sole briefing occurred on January 22, the day after the Senate confirmed her to the post. On that date, as the nation’s top diplomat, Clinton signed a document acknowledging she received a security briefing.

“I hereby acknowledge that I have received a security indoctrination concerning the nature and protection of SCI,” or the nation’s highest classified materials, was part of the pledge in the document.

But there is no evidence that she received any briefings after that, according to the documents provided to TheDCNF by the State Department. The department’s Foreign Assistance Manual requires all State Department employees to receive regular security training at least once a year. (RELATED: Hillary Faces National Security ‘Uprising’ Over Emails.”)

The annual briefings are essential to the maintenance of security for classified information and documents because the cyber and other threats continually change over time, as hackers and foreign intelligence elements develop new methods of attack, according to experts interviewed by TheDCNF.

A former senior State Department official told TheDCNF there should be official certification for Clinton’s briefings for all four years.

“There should be at least a memorandum for the record by the person who administered the oral briefing each year,” the former official, who requested anonymity, told TheDCNF late Thursday.

Ordinarily, he said, a senior State Department official “should have put something in the record.” He emphasized that yearly oral security briefings for the Secretary of State were common while he was in the department.

The official said the fact there was only a certificate for a single year of a briefing was “inconsistent with the practices” at the department. (RELATED: Will Hillary’s Former IT Guru Be The Star Witness Against Her?).

“It is certainly inconsistent with practices as I have known it for cabinet members,” he said. “If there is only one instance of her being briefed and nothing for the next four years, then I would consider that to be a lapse in security protocol, even at that level. Even the secretary needs to be reminded from time to time.”

“Someone was responsible for making sure that she was compliant with the various rules and regulations,” he said. “And if there’s no record of that, that probably means it didn’t happen.

“I suppose it’s possible that that information is sitting in a file that just hasn’t been searched. I know having done lots of FOIA and other kinds of congressional document requests over the course of my time there. But if there’s no such document, that constitutes a lapse.

He said Clinton should have “led from the top” by demonstrating that she was serious about security.

“You set standards from the top,” he said. “So if you show that even the secretary is taking the security rules and regulations and procedures very seriously and doing everything in their power to abide by them in the appropriate way, that sends a signal to everybody else that they have to treat it the same way.

“But once you start down the road that, well, ‘I’m special and this is inconvenient,’ that sends a different signal to the work force,” he said.

National security officials have been surprised by the many measures Clinton undertook that undermined communications and information security protections while she was Secretary of State.

Her unorthodox activities include her decision to operate a private email server in her home for official government business and repeatedly pressing the National Security Agency to override rules barring her from using her unsecured Blackberry phone in her office wing.

“Who decided she would only get that one-time briefing? That almost sounds as if it’s a culture issue within her organization,” Col. James M. Waurishuk, a retired senior intelligence officer with 30 years of military and intelligence experience, told TheDCNF.

“I can’t imagine what went through her mind. There’s no excuse,” he said.

Waurishuk also served as deputy director for intelligence for U.S. Central command and a staff member at the White House National Security Council.

In a press briefing Thursday, State Department spokesman Mark Toner told reporters that cyber awareness training for all officials, including the Secretary of State, is mandatory. “It’s my understanding that the Secretary of State, everybody in this building, would receive that type of training and awareness,” he said.

“We all have to undergo through that,” he added. “It’s considered mandatory.”

“Knowing the things that what we now know what she was doing, you would think she would want to have that documentation available should she ever be questioned,” noted Waurishuk. “Unless she believed that no one was ever going to question her on anything she’s doing,” he added.

TheDCNF filed a Freedom of Information request with the State Department Jan. 29, 2016, that sought documents “memorializing certification that senior State officials had satisfied mandatory security training courses regarding the handling of classified materials and communications through secure equipment.”

The FOIA request also sought documents showing that Clinton had “satisfied mandatory Information Technology training courses.”

The request covered Clinton’s entire term during her four year tenure. TheDCNF asked for certifications held by the Foreign Service Institute, the Department of Security Services, the Bureau of Information Resource Management and the Office of Security.

TheDCNF sued the State Department in U.S. District Court for the District of Columbia to force release of the documents. The case was handled by the Justice Department’s civil division.

Separately Thursday, the non-profit government watchdog Judicial Watch released additional documents showing that Clinton repeatedly and fruitlessly sought to bring into her secured Secretariat wing a commercially produced Blackberry cell phone that has been banned for decades.

[dcquiz] National security attorney Mark Zaid handled the FOIA request for TheDCNF when it became necessary to take the government to court to secure release of the documents.

Zaid said, “I think it raises questions as to the level and extent of security training that the Secretary of State might have received. There needs to be a degree of showing leadership from the top to ensure that proper security protocols are in place and implemented. We’re not seeing, at least by way of documentation, evidence that that was the case.”

A Clinton spokesman has been asked for comment.

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