## 2 Literature Review
The environment in which authentication takes place can also be a factor. Some of the environments mentioned in the table include cloud computing, private cloud storage, cloud storage in smart banking, users' metadata in a multi-cloud, cloud-based logistics IS, cloud-based OTP services, multiple agents cloud-based search engines, cloud health care, cloud-based SDN health care, and cloud-based financial transactions. MFA is especially important in cloud computing, where data and applications are often hosted by third-party providers. When using MFA, cloud environment can reduce the risk of unauthorized access to their cloud resources, even if an attacker is able to obtain a user's password. Organizations can choose to implement MFA for all cloud users or only users, such as those with access to sensitive data. MFA can be implemented at the cloud provider level or at the application level. Some of the benefits of using MFA in cloud computing are presented as follows. * Reduced risk of data breaches: MFA makes it much more difficult for attackers to gain access to cloud resources, even if they have compromised a user's password. * Improved compliance: Many industry regulations require organizations to implement MFA for certain types of data and applications. * Enhanced user experience: MFA can be implemented in a way that is convenient for users, such as by using push notifications or smartphone apps. Therefore, MFA is an essential security measure for cloud computing environments. When using MFA, the risk of data breaches will reduce, improve compliance, and enhance the user experience. According to our survey, the MFA either used as 2 FA, 3 FA, or more. It is used either beside other techniques such as cipher text-policy attribute-based encryption (CP-ABE) [42; 43], SSO [46], RSA algorithm and hash functions [50], SHA 1 and AES-128-CBC [38], AES 256 [74], pre-shared secret keys (PSK) [48], deep learning and leap motion controllers [83], enhanced Feistel block ciphers [59; 60], Blockchain [61; 63; 65], VGG face models [44], CNN-LSTM-based classifiers, [70], and semantic ambient media frameworks (SAMF), which is an authoritative interface between smartphones and public displays [73]. A different number of factors are used, ranging from two to five. The most used factors are Username and Password, OTP, and Biometrics of the user. These biometrics include fingerprints, face verification, and iris. Other factors include location confirmation and temporal data confirmation [47], security questions [65], graphical passwords [67; 68], motion signals of in-air-handwriting [71], the geometry of the hand skeleton [71], keystroke rhythm [72], hand gestures [83], and image recognition with user-established relations [84]. In this paper, we proposed an interactive, flexible, and secure multi-factor multi-layer authentication framework by designing an authentication method selector (AMS) and interactive intrusion detection steps. AMS is based on a pool that contains a variety of authentication techniques and knowledge of previous user authentication information. Depending on the needs of the organization, the administrator will be able to add the proper authentication mechanism. The administrator will select an authentication method from the pool and activate it in accordance with these specifications. The proposed framework provides interactive intrusion detection steps via the inspection of user behavior based on the user's previously used location and web browser. This framework provides a flexible and inexpensive authentication method based on the AMS technique and intrusion detection systems.