Malware proliferation and sophistication have drastically increased and evolved continuously. Recent indiscriminate ransomware victimizations have imposed critical needs of effective detection techniques to prevent damages. Therefore, ransomware has drawn attention among cyberspace researchers. This paper contributes a comprehensive overview of ransomware attacks and summarizes existing detection and prevention techniques in both Windows and Android platforms. Moreover, it highlights the strengths and shortcomings of those techniques and provides a comparison between them. Furthermore, it gives recommendations to users and system administrators.