The best recommendation to prevent unauthorized access to cloud-based applications and data is to implement multi-factor authentication (MFA). MFA is a method of verifying the identity of a user by requiring two or more pieces of evidence, such as a password, a code sent to a phone, or a biometric factor. MFA adds an extra layer of security to prevent unauthorized access, even if the user's password is compromised or stolen. MFA can also help comply with data privacy and security regulations, such as the General Data Protection Regulation (GDPR) and the Health Insurance Portability and Accountability Act (HIPAA).
The other options are not as effective as MFA in preventing unauthorized access. An intrusion detection system (IDS) is a tool that monitors network traffic and alerts administrators of suspicious or malicious activity, but it does not prevent access by itself. Updating security policies and procedures is a good practice, but it does not ensure that users follow them or that they are enforced. Utilizing strong anti-malware controls on all computing devices can help protect against malware infections, but it does not prevent users from accessing cloud-based applications and data from any Internet-connected web browser.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019, p. 2471
* ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription2
* What Is Cloud Security? | Google Cloud3
* 5 Cloud Application Security Best Practices | Snyk4