A cyber-physical system (CPS) consists of a large number of geographically dispersed entities and distributed data sharing is necessary to achieve network-wide goals. However, distributed data sharing also raises the significant concern that private or confidential information of legitimate entities could be leaked to unauthorized entities. Privacy has become an issue of high priority to address before a certain CPS can be widely deployed. Existing privacy-preserving techniques solely focus on the cyber space but ignore the physical world, and hence they alone may not be adequate to ensure CPS privacy. This paper aims to summarize recent studies on how to develop control-theoretic approaches to complement existing privacy-preserving techniques and ensure CPS privacy.