useful

/ˈyüs-fəl/

adjective

  1. capable of being put to use; especially : serviceable for an end or purpose

  2. of a valuable or productive kind

noun

  1. a naive or credulous person who can be manipulated or exploited to advance a cause or political agenda

It is one task of the KGB [in 1982] to apply its skills of secrecy and deception to projecting the Soviet party's influence. This it does through contacts with legal Communist Parties abroad, with groups sympathetic to Soviet goals, with do-gooders of the type that Lenin once described as “

noun

  1. the amount of time during which something is in good enough condition to be used

the useful life of a satellite