The study shows that in the People's Republic of Hungary, within the frames of the mono-party system, the state security service—functioning according to the directives of the ruling communist party—was keen on trying to hinder the influence of Western ideologies from corrupting the youth through popular music. This fight was going on from the early '60s through 1990, the year that brought about the change of the political system, the transition from dictatorship to plural democracy, from planned economy to free market. To achieve their goal, to influence the functioning of the institutional system of popular music and to break the popularity of several beat/rock/folk/punk groups considered subversive, the secret service used—among other means—a web of informants. In doing so they could have some success, but in the end—due to the lucky turns of world politics—they just were not able to stop the collapse of the system. For the historian, however, these reports give a fascinating insight into the life of the young generation under state socialism and the moral ambiguities of resistance, co-existence and collaboration.