Edward Snowden, a former technical worker at the CIA who sensationally revealed himself as the whistleblower behind leaks that uncovered secret US government surveillance programmes is part of a long history of whistleblowers who risked their lives and careers to make secret information public.
Most famous of all is Deep Throat, the source for the Washington Post's Watergate scandal that brought down President Richard Nixon.
His identity was revealed 30 years later as the former FBI Number Two Mark Felt.
But many whistleblowers in recent times have chosen to go public with their identities immediately, like Big Tobacco whistleblower Jeffrey Wigand and former New York City Detective Frank Serpico testified against police brutality and corruption.
Many have been imprisoned for the information they released, like Israeli nuclear whistleblower Mordechai Vanunu and WikiLeaks source Bradley Manning, who faces the possibility of life in prison.
