CNN News:特朗普取消前CIA局长布伦南安全许可

A former Director of the CIA has lost his Security Clearance. To help us explain what exactly happened and the controversy surrounding it, here's cnn's Tom Foreman.
TOM FOREMAN, cnn CORRESPONDENT: More precisely are security clearances and where do they come from? Security clearances are issued by many government agencies and can come in several different levels offering different access to sensitive or classified material. And even if you have the highest level of clearance, that's not an invitation to plunder all files. You will likely see only materials you need to know about. Who gets security clearances? As a practical matter, they go to people who are intimately involved in the safety and defense of the United States and its allies.
Now this is not all military business. For example, there could be economic information or infrastructure details or negotiations with other countries which might considered highly sensitive and fall under this umbrella. But all this has to do with active government service so why should anyone who's left the government retain his or her security clearance? Former employees of an agency have experience. They have institutional knowledge and the people who take over for them may need that. Say you worked on some classified matter involving another country and a new team comes in, they need to know what you did. This would assist the new team to be able to talk to you about the current situation as well.
In addition, some private industries, defense contractors for example, do work that requires private citizens to deal with sensitive government matters. So having a security clearance outside the government can also be useful. So why would anyone lose or have their security clearance revoked.
Usually that happens because they truly no longer need it or some conflict has arisen. For example, they start working for a foreign hostile government or they just get into trouble. They commit a crime or their linked to some illicit or risky activity.

AZUZ: U.S. President Donald Trump took away the security clearance of former CIA Director John Brennan last week. Brennan served in the CIA under the Obama Administration. In recent years, he's very critical online and on TV of President Trump. Following his decision to revoke Brennan's security clearance, the President said Brennan made mistakes as CIA Director and that he's using his status as a former high ranking official to make quote "unfounded and outrageous allegations about the Trump Administration".
Former Director Brennan says President Trump is abusing his power and punishing his critics. And more than 12 other former intelligence officials called the move an attempt to stifle free speech. Republican Senator Mitch McConnell says Donald Trump has the authority to revoke security clearances. And officials say the President's reviewing the clearances of other people who served in the Obama Administration.