A federal criminal investigation has also been opened.
As best as the CIA can determine, this is the first time it has ever fired one of its officers for unauthorized contacts with reporters, CBS News correspondent Jim Stewart reports.
Officials would only identify the fired officer as a female who had "acknowledged a pattern of discussions ... with more than one reporter," Stewart adds.
CIA spokesman Paul Gimigliano said an officer had been fired for having unauthorized contacts with the media and disclosing classified information to reporters, including details about intelligence operations.
"The officer has acknowledged unauthorized discussions with the media and the unauthorized sharing of classified information," Gimigliano said. "That is a violation of the secrecy agreement that everyone signs as a condition of employment with the CIA."
Citing the Privacy Act, the CIA would not disclose any details about the officer's identity or what she might have told the news media.
However, a law enforcement official confirmed there was a criminal investigation under way and said the CIA officer had provided information that contributed to a Washington Post story last year saying there were secret U.S. prisons in Eastern Europe. The law enforcement official spoke only on condition of anonymity, citing the sensitivity of the matter.
The Post reported that the CIA had set up a covert prison system after Sept. 11, 2001, that at various times included sites in eight countries. The story, and government officials have said it did significant damage to relationships between the United States and allied intelligence agencies.
CIA Director Porter Goss has pressed for aggressive investigations of leaked information.
"The damage has been very severe to our capabilities to carry out our mission," Goss told Congress in February, adding that a federal grand jury should be impaneled to determine "who is leaking this information."
On Friday, another government official, also speaking on condition of anonymity because of the sensitivity of the information, said the fired officer had failed a polygraph test.
It was not clear if the person was taking a routine polygraph examination, as is required periodically of employees with access to classified information, or if the polygraph was among those ordered by Goss to find leakers inside the agency.
Justice Department officials declined to comment publicly on the firing and whether the matter had been referred to federal prosecutors for possible criminal charges. One law enforcement official said there were dozens of leak investigations under way.
The Washington Post's Dana Priest won a Pulitzer Prize this week for her reporting on the secret prisons story.
"No Post reporter has been subpoenaed or talked to investigators in connection with this matter," Post spokesman Eric Grant said Friday.