Best Practices for Preventing Malware on IaaS Compute Instances

C.

Out of the given options, the BEST approach to prevent users from running malware on several IaaS compute instances is to implement an application whitelisting policy (Option C).

Application whitelisting is a security model that only allows specific, authorized applications to run on a system while blocking all other applications. This approach provides a way to control which applications can be executed on a system, thereby reducing the risk of malware infections.

Here are the reasons why the other options may not be as effective as implementing an application whitelisting policy:

A. Encrypt all applications that users should not access: Encryption is a technique to secure data by encoding it in a way that only authorized parties can read it. Encrypting applications that users should not access will not prevent them from running the applications. Instead, it will make it difficult for users to read and modify the application code, which is not the objective of preventing malware.

B. Set the execute filesystem permissions on the desired applications only: Setting the execute filesystem permissions on the desired applications only will prevent users from running the undesired applications. However, it will not prevent them from copying the executable files and running them on another system, where the filesystem permissions may not be enforced.

D. Disable file sharing on the instance: Disabling file sharing on the instance will prevent users from sharing files between different systems. However, it will not prevent them from running malware on the same system where file sharing is disabled.

Therefore, the best option is to implement an application whitelisting policy as it provides the most effective approach to control which applications can be executed on the system, thereby reducing the risk of malware infections.