Espionage or spying involves an individual obtaining information that is considered secret
Secrecy is the practice of hiding information from certain individuals or groups, perhaps while sharing it with other individuals...

 or confidential without the permission of the holder of the information. Espionage is inherently clandestine
Clandestine operation
A clandestine operation is an intelligence or military operation carried out in such a way that the operation goes unnoticed.The United States Department of Defense Dictionary of Military and Associated Terms defines "clandestine operation" as "An operation sponsored or conducted by governmental...

, lest the legitimate holder of the information change plans or take other countermeasures once it is known that the information is in unauthorized hands.

Espionage is usually part of an institutional effort by a government
Government refers to the legislators, administrators, and arbitrators in the administrative bureaucracy who control a state at a given time, and to the system of government by which they are organized...

 or corporation, and the term is most readily associated with state
Sovereign state
A sovereign state, or simply, state, is a state with a defined territory on which it exercises internal and external sovereignty, a permanent population, a government, and the capacity to enter into relations with other sovereign states. It is also normally understood to be a state which is neither...

 spying on potential or actual enemies primarily for military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...


And we did have fun. For five years we bugged and burgled our way across London at the State's behest, while pompous bowler-hatted civil servants in Whitehall pretended to look the other way.

Peter Wright|Peter Wright, "Spycatcher" (Heinemann, 1987), p. 54

Because something is not what it is said to be, Ma'am, does not mean it is a fake. It may just have been wrongly attributed.

A Question of Attribution|A Question of Attribution by Alan Bennett|Alan Bennett.

The spies of the underworld are legion. Craven crooks, for the most part, they are prey to blackmail.

"Camp 020: MI5 and the Nazi spies" (Public Record Office, 2000), p. 106

To MI5, if you steam this open you are dirty buggers.

Peter Wright|Peter Wright, "Spycatcher" (Heinemann, 1987), p. 46

what is espionage but the very thing we exercise daily in our lives?

John Le carre