Whistleblower is a term which refers to those who call out illegitimate activity.  Contexts vary in which this might occur, and so nuance may be required, but the fundamental point is that transparency of information should be the default for an effective democracy.  Recently there have been a number of whistleblowers prosecuted by the Federal Government.  For more information on these, refer to Stop the War on Whistleblowers.  This site also provides the option for signing a petition requesting the government to be more supportive of whistleblowers.