Most of the current reputation models suffer from some common vulnerabilities. This means that malicious agents may be able to perform attacks that exploit these vulnerabilities, which has the potential to cause much harm such as monetary losses and to place the whole system in jeopardy. In this chapter we detail some of the most important vulnerabilities of current reputation models. We also detail examples of attacks that take advantage of these vulnerabilities in order to achieve strategic manipulation of reputation models. Moreover, we review works that partially/fully address these vulnerabilities, and thus, prevent possible attacks from being successful.