§ 3 HDSIG
Processing of Personal Data, Processing on Behalf
(1)The processing of personal data by a public body shall be permissible where it is necessary for the performance of the task within the competence of the controller or in the exercise of official authority vested in the controller.
(2)Persons and bodies that carry out maintenance work and comparable ancillary activities in connection with the processing of personal data on behalf of a controller shall also be deemed to be processors. zur Einzelansicht § 3