In the era of big data, the balance between network security and personal privacy has become a key issue. This paper analyzes the new connotation and threat of network security, and discusses the ethical conflict between network security and personal privacy. Then it puts forward four principles to determine the ethical boundary. Finally, the guarantee mechanism is constructed from the aspects of perfecting laws and regulations, applying technological innovation, enhancing the awareness of ethical education, and self-discipline supervision and management in the industry. Taking the new power tram enterprises as an example, it is emphasized that enterprises should pay attention to balance and establish a standardized mechanism to eliminate the risk of conflict and realize the harmonious development of digital society.