sleeper (sleeper agent)

An agent who lives in a foreign country as an ordinary citizen and becomes active only when a conflict situation arises.

Definition based on the International Spy Museum glossary, which also mentions sleeper cells. What sets a sleeper apart from an ordinary agent is that for a long time they do nothing at all – their value lies in being ready to act in the future.¹

The concept is close to that of an illegal, although not every illegal is a sleeper. In the 2010 case the US Department of Justice described the defendants as accused of carrying out long-term, “deep-cover” assignments on behalf of Russia: they had lived for years in the United States under false identities, and their tasks were to include recruiting sources and gathering information. On 28 June 2010 the department announced the arrest of ten of the 11 defendants, stressing that the charges were merely allegations.^2,3