The Senate Judiciary Committee confirmed Friday that former Secretary of State Hillary Clinton's security clearance has been revoked by her own request. The move comes more than a year after Judiciary Committee chairman Chuck Grassley requested the department to investigate if Clinton still had security clearance.

According to the letter released by Grassley, the State Department said that Clinton's clearance was revoked on Aug. 30. Five of Clinton's aides, who she had asked be designated as researchers, had their security clearances revoked on Sept. 20.

During Clinton's run for president, lawmakers and investigators looked into her and her staff's security clearance as part of the investigation into her use of a private email server.

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Retiring senior officials usually retain a basic level of security clearance, but the Trump administration has been "exploring" the possibility of revoking security clearances of several intelligence officials who have criticized the president.

Press secretary Sarah Huckabee Sanders said in July that the White House is evaluating on a "case by case basis" the clearances of several of President Obama's intelligence officials, including former FBI director James Comey and former National Security Adviser Susan Rice.

In August, President Trump ordered former CIA Director John Brennan, one of those officials, be stripped of his security clearance.

The CIA "holds" former directors' security clearance and renews it every five years for the rest of their lives. But that requires former CIA directors to behave like current CIA employees if they want to keep their clearance, which means avoiding travel to certain countries and generally living in a manner above reproach.

Other former government employees can keep their security clearances if they move to a private sector job where they work with classified information, such as at a defense contractor. The company would then apply to the government for someone to keep or receive a security clearance. The security officers at the different agencies then grant or rule if someone can keep their clearances.

Hundreds if not thousands of private companies apply for their employees to receive security clearances. In an interview with Bloomberg earlier this year, the CEO of Lockheed Martin said that 60,000 of her employees have a security clearance of some kind.