Eric Schmidt. Eric Schmidt / Twitter Google chairman Eric Schmidt and former svp/product management Jonathan Rosenberg wrote a book about management called "How Google Works." In it, they talk about all the things they learned running the world's biggest search engine.

At a talk in London last year, the pair revealed what they looked for when hiring new people at the company.

But sometimes Google needs to get rid of people, too, especially when a staffer isn't a good fit with the company's culture. Rosenberg said the company was constantly on the lookout for "knaves," or employees who are so annoying or ill-willed that they drive away the good employees. Too many knaves can cripple a company, Rosenberg says, so preventing a high "knave density" — the level of antagonistic employees concentrated in any one team — is crucial. "If you get more than a few of these knaves, people don't want to come to work in the morning," he said.

So what does a knave look like?

Knaves "lie, cheat, steal, and take credit for other people's work," Rosenberg said. He also said knaves "leak."

That last bit was interesting, and it may help explain why, despite the fact that Google has roughly 48,000 employees, the company's staff members rarely talk to the media.

Here's the passage from the book that talks about the danger of knave density: