Abstract: Social networks (SN) have the characteristics of immensity of data, huge clientele, openness in information sharing, difficult customer relationship management, etc. Security issues, such as privacy protection, identity authentication and data access control have increased enormously on such networks. The basic concept, present development and main technology of SN were introduced. And specific security risks according to its characteristics were also summarized from the aspects of data mining, traditional threats and identity theft on SN. Furthermore, several existing security solutions of SN were described, and their working principles were analyzed and compared. Finally, some hot security research topics were given and the future research directions were discussed.

Key words: social network security, privacy protection, identity authentication, access control