Generally speaking, the traditional approach of security mainly regards states as a sole referent object of security and refutes any attempt to broaden the concept of security. This understanding is known as a realist approach. This approach, however, has been recently challenged by the Copenhagen School, the Welsh School, and the human security approach. The Copenhagen School assumes that there is now a duality of security: state security and societal security. However, both the Welsh School and the human security school look at individuals as a sole referent object of security. This article critically reviews the traditional approaches of security, the Copenhagen School, the Welsh School, and the human security approach. This article finally argues that the Copenhagen School could successfully broaden the concept of security, and therefore, it is more convincing when compared to other schools.