A method and apparatus for ensuring security of a session. In the method, a first client selects a user interface related to a process in need of security from among user interfaces related to predetermined contents provided from a first server, and a first client or a second client communicates directly with a second server operated by a contents provider to perform the process in need of security and notifies the first server of the performing result. Thus, it is not required to transmit/receive security information via the first server.