Portable devices are today used in all areas of life thanks to their ease of use as well as their applications with unique features. The increase in the number of users, however, also leads to an increase in security threats. This study examines the threats to mobile operating systems. Addressing the four mobile operating systems (Android, Apple OS (iOS), Symbian and Java ME) with the highest number of users, the study provides statistical information about the features of the corresponding operating systems and their areas of use. In the study, the most important threats faced by the mobile operating systems (Malware, Vulnerabilities, Attacks) and the risks posed by these threats were analyzed in chronological order and the future-oriented security perspective was suggested..