The present research investigates the opinions of employees of Piraeus Bank, regarding the characteristics of internal audit that are important and their level of implementation to be considered effective. Additionally, the internal audit strategies used to prevent fraud were studied, taking into consideration the location of the banks. Methodologically, a questionnaire was distributed via Google Forms to a total of 103 employees of Piraeus Bank, using a stratified sampling method. The findings highlighted a gap between the employees’ perceived importance of certain internal audit characteristics and their actual implementation, such as the independence of internal auditors and their access to necessary information. Moreover, the research revealed that avoiding fraud does not rest upon one single strategy, but it needs a collective implementation of measures that are actually effective. It was also revealed that branches which apply fraud-preventing measures at a lower level are facing fraud more often. Lastly, the research showed that urban and semi-urban branches apply the recommended practices to prevent fraud intensively compared to bank branches in villages and islands of Greece.