RESUMEN: el presente trabajo, parte de una aproximación etnográfica a un Combo de la ciudad de Medellín, perteneciente a la zona nororiental y con control en el barrio Santa María, en dónde se ha establecido una relación de interacción constante entre este grupo y los habitantes del lugar, ya que son legitimados y apoyados por el cobro de un aporte voluntario o vacuna, por el servicio de vigilancia que ellos prestan al interior de la comunidad, como una alternativa al mismo control y servicio que para ellos representa la seguridad del barrio donde realizan la venta y consumo de drogas.ABSTRACT: this work approaches, through the ethnographic method, the dynamics surrounding a gang (or 'combo') from northeast Medellin: its presence, control and interaction with the people of the Santa María neighborhood. Within this interaction, a sort of validation to the group's presence has been taking place, since they obtain their funds from the same people they're trying to control, through voluntary contributions aswell as forced contributions, also known as 'vacunas'. These contributions are justified by the service this combo provides, which is a vigilante-style private surveillance, something that is also convenient to the group's interest, as they are the ones in charge of the drug distribution within the area, a task that requires security for the spot that it takes place on.