The security of oPass: A User Authentication Protocol Resistant to Password Stealing and Password Reuse Attacks proposed by H.M.Sun et al. in IEEE Transactions on Information Forensics and Security, Vol.7, No.2, April 2012 is analyzed. Upon completion of the analysis of the paper, four kinds of attacks SMS service, attacks on oPass communication links, unauthorised intruder access using the master password and Network attacks on untrusted web browser are identified in different scenarios. Thus, we proved that oPass proposed by H.M.Sun et al. is not suitable for practical application.