Oversharing on Facebook is posing a unique challenge for the CIA's recruitment of future spies.

Every year, the agency has to drop five or six stellar candidates because of things they said on social media networks like Facebook (FB), Twitter (TWTR) and LinkedIn (LNKD), the CIA's top recruiter said in an exclusive interview with CNNMoney.

That's a tiny fraction of the 20,000 applicants who make it into the final phases of the interview process. But the CIA has rescinded job offers because of their social media posts.

"Obviously, secrecy and social media are at odds with each other," said CIA hiring chief Ron Patrick, who keeps a vague LinkedIn account -- and has Facebook and Twitter accounts under a different name.

Want to work at the CIA? Here's Patrick's advice.

Don't like us on Facebook.

"Once we've expressed some serious interest in their application we say: Don't follow us, don't like us. And if they have, we asked them to back off a bit," Patrick said.

It's all right to express interest publicly -- at first. But you might be an undercover CIA operative in a war zone someday. Don't keep broadcasting your interest in spying to the world.

However, do have a presence on social media.

Secret agents aren't antisocial or technophobic.

"If we only hire people that are afraid of it, they're not going to be much help to us in the world or our mission," Patrick said. "Many of the people we're dealing with -- especially the targets we're working against -- are on social media."

Don't announce a great interview.

As cringe-worthy and glaring as this is, this one has derailed great candidates. Once you apply to the CIA, the agency tells you to shut up. Some don't get it.

Patrick said several aspiring spies have made it all the way to a face-to-face interview, then they go online and post something like, "I interviewed with CIA! Dynamite interview!"

"It's a question of trust and integrity," he said. "They can't follow instructions and handle the severity and importance of the job they've applied to."

Don't crowdsource cheating tips.

Last year, the CIA had to withdraw a job offer when someone made this stupid mistake.

The screening process for a clandestine officer position is long and complicated. These are the spies who typically work overseas, recruiting tipsters and reporting sensitive intel back to their bosses at headquarters.

One man made it all the way through and even got the CIA job offer, Patrick recalled. Then a background investigator for the agency asked him if he'd used social media in the application process.

Yes, he admitted. He was nervous about passing the polygraph (lie detector) exam, so he used his network to track down specific people who could help "defeat the polygraph," Patrick said.

"As soon as he said that, we immediately disqualified the person," he said.

Once you're in, don't tag fellow officers at a party.

This is an unspoken rule. CIA employees tend to operate in little, private bubbles. You don't typically know what your desk neighbor is really working on. So, you don't know if snapping their photo at a party will blow their cover.

No face tagging -- or announcing their location either. It's not nice to @JackRyan. Besides, adding coworker spies to your "friends" list only makes it easier for foreign intelligence agencies to map out the CIA network.

"The word discretion is not a bad word around here," Patrick said.

If you're hired, don't disappear from social media.

"It's funny. People who've done that were posting in Omaha, then New York -- then they stop talking," Patrick said. "It's going to raise suspicion. That's a clue. It's a sign that other intel services might look at."