Security-related issues are creeping in almost every authentication problem. Even the secured systems may be exposed to unknown attacks. While addressing one aspect of security, one tends to forget how vulnerable our system is to other attacks. Therefore, it is necessary to understand the impact of these attacks completely and also to get a vision of the hazard they may put when combined together. In this chapter, the authors focus on two such attacks on iris biometric: replay attack and template attack. They provide a detailed analysis of current research work on each of it individually. The comparative study of solutions to these individual attacks is done with the techniques that aim at combining these two attacks. The authors clearly bring out the advantages of the latter approach, which is the driving force in need for a shift to more innovative ideas.