From the point of use and deployment of new media, the relationship of the employer to the current or potential employee has changed dramatically. Especially the recent development has led to an increase in the level of control. This thesis should be about the limits of the possible control of the employer to his employees, especially in relation to the determination of processed data. Referring to the initiation of an employment relationship the limits of the right to ask questions of the employer, the duty of the employee to disclosure important things and the requirement of gaining information by third parties is an essential aspect. In the while working relationship, the level of control or the forms of information gathering by the employer will be investigated through the detailed regulation of the Data Protection Act 2000. Moreover, the instruments of collective rights protection of the ArbVG set limits because of the participation rights of the work council. Concerning the protection of privacy rights the§ 16 Civil Code is also of considerable importance. Furthermore the increased use of social networks has led to a rise out of the employer's control, especially of workers transparency. As a result there is because of the timeliness of the issue in relation to the ever-increasing role of social networks an absence in the jurisprudence and literature. Because of this, the links to similar topics are given in this thesis to derive furthermore conclusions.