With the continuous improvement of national economic construction, the living standard of Chinese residents has been rising steadily. The application of information technology has penetrated into every aspect of people's production and life, and the amount of data production has grown exponentially, marking the advent of the era of big data. In the era of big data, computer network bears the important responsibility of collecting, storing and transmitting information. However, with the increasing dependence of Chinese residents on computers and the Internet, problems also follow. Nowadays, network security problems are frequent and information leakage is severe. Almost everyone has experienced the experience of personal information being leaked online and suffered losses to a greater or lesser extent. This paper analyzes the source of computer network security problems in the era of big data and puts forward effective preventive measures.