A CIA NOC is an agent who works with a non-official cover and without obvious ties to the U.S. government. NOC agents who work in foreign countries are in more danger than agents with official cover, because they do not have the protection of diplomatic immunity if they are caught.
Most CIA overseas operatives work with the State Department and undertake diplomatic duties to disguise their espionage activities. This provides them with an easily established cover and legal protection if they are caught. However, NOC agents work ostensibly as businessmen, bankers, scientists, academics or members of non-government organizations. Sometimes, NOC agents are employees of existing U.S. multinational companies, while under other circumstances, the CIA creates an entire organization solely for providing cover for its operatives. For instance, Air America was an airline founded by the CIA to conduct intelligence work in China, Vietnam, Laos and Cambodia.
Because establishing a CIA NOC agent in a foreign country is so difficult, expensive and dangerous, once a cover is established, it is kept clandestine and maintained for a long time, sometimes decades. The CIA protects the anonymity of NOC agents as carefully as possible. To maintain the credibility of NOC agents, the CIA falsifies business papers, salary checks, tax records, personnel files and phone lines. Often NOC agents do not reveal their real jobs, even to close relatives.