The former CIA director revealed publicly for the first time that he was "concerned" about contacts between Russian officials and people involved in the Trump campaign.
The former CIA director described for the first time a tense phone call he had with the head of Russia's security service in August.
Brennan has said he doesn't think President Trump "has a full appreciation of Russian capabilities."
U.S. intelligence officials fear a mole exposed CIA spying operations in China, but American embassy employees have been targeted for years.
A New York Times report claimed that Beijing killed at least 12 CIA sources between 2010 and 2012.
The 'New York Times' reported that China killed or imprisoned 18 to 20 CIA sources from 2010 to 2012. Investigators remain divided over whether there was a spy within the CIA who betrayed the sources or whether the Chinese hacked the CIA's covert communications system
North Korea has ratcheted up its rhetoric over an alleged plot from the U.S. and South Korea to kill leader Kim Jong Un.
Russia will not want to be the only great power in warring Syria after ISIS is defeated.
Franklin D. Roosevelt wanted art to help build appreciation for Arab culture and counter pro-Israel influence on U.S. foreign policy.
The former Republican congressman said the whistleblowing group is a tool used by Russian military intelligence.
No country allows limitless "quasi-freedom" online, the Russian leader said.
For decades, Beijing has principally targeted Chinese-Americans as potential spies. Now it has cast a wider net—creating fear and paranoia at Langley.
All 10 airports targeted by the laptop ban are located in Muslim-majority countries.
Trump made explosive accusations amid a Russia scandal in his administration.
WikiLeaks, not the CIA, is the most responsible for reducing the world's cybersecurity.
WikiLeaks Editor Julian Assange was speaking at a press conference from London's Ecuadorian embassy.