Nowadays big data has become a hot topic in both the academic and the industrial research. It is regarded as a revolution that will transform how we live, work and think. However, there are many security risks in the field of data security and privacy protection when collecting, storing and utilizing big data. Privacy issues related with big data analysis spell trouble for individuals. And deceptive or fake information within big data may lead to incorrect analysis results. This paper summarizes and analyzes the security challenges brought by big data, and then describes the key technologies which can be exploited to deal with these challenges. Finally, this paper argues that big data brings not only challenges, but also technical revolution in the field of information security.