Secret police forces are typically associated with totalitarian regimes, as they are often used to maintain the political power of the state rather than uphold the rule of law. Secret police are law enforcement agencies typically endowed, sometimes officially, with authority superior to other civil police forces, typically operating outside the normal boundaries of the law, and they are often accountable only to the executive branch of the government. They operate entirely or partially in secrecy, that is, most or all of their operations are obscure and hidden from the general public and from all government officials, except for the topmost executive officials.
Secret police agencies have often been used as an instrument of political repression.
States where the secret police wield significant power are sometimes referred to as police states. Secret police differ from the domestic security agencies in modern liberal democracies, because domestic security agencies are generally subject to government regulation, reporting requirements, and other accountability measures. Despite such overview, there still exists the possibility of domestic-security agencies acting unlawfully and taking on some characteristics of secret police.
Which government agencies may be classed or characterised, in whole or part, as "secret police" is disputed by political scientists.
People apprehended by the secret police are often arbitrarily arrested and detained without due process. While in detention, arrestees may be tortured or subjected to inhumane treatment. Suspects may not receive a public trial, and instead may be convicted in a kangaroo court-style show trial, or by a secret tribunal. Secret police known to have used these approaches in history include the secret police of East Germany (the Ministry for State Security or Stasi) and Portugal (PIDE).
Secret police have been used by many types of governments. Secret police forces in dictatorships and totalitarian states usually use violence and acts of terror to suppress political opposition and dissent, and may use death squads to carry out assassinations and "disappearances". Although secret police normally do not exist in democratic states, there are different varieties of democracy and, in times of emergency or war, a democracy may lawfully grant its policing and security services additional or sweeping powers, which may be seen or construed as a secret police.