Ransomware is a program used by an attacker or hacker, that locks or encrypts target files or data. The user or the owner of data cannot access these without the explicit assistance of the attacker. After locking or encrypting, the attacker demands ransom generally in the form of cryptocurrencies to permit user to regain access to the locked data. However, there is no guarantee that the user can access seized data again even after that ransom has been paid. Researchers have proposed various tools and techniques to protect and fight against ransomware. Existing tools and methods are not sufficient to detect ransomware early because several new ransomware variants are being introduced every day. Machine learning techniques are used efficiently in various applications like ransomware detection, spam detection, text classification, pattern recognition, etc. Further, deep learning, a subfield of machine learning, eliminates the burden of re-engineering the features for the new types of malware or network attacks that may arise. In this paper, several machine learning-based detection techniques against ransomware are reviewed.