The best approach to preventing the recurrence of a security threat is to assign a policy that directly addresses the security posture of your storage accounts, particularly with regard to public accessibility. By disallowing public access to storage accounts, you significantly reduce the attack surface that can be exploited by malicious actors.
Storage accounts that are publicly accessible can be a target for various types of attacks, such as data exfiltration or unauthorized access to sensitive information. By implementing a policy that enforces the disallowance of public access, you are actively mitigating this risk. This proactive measure ensures that only authorized users and applications can access the storage accounts, thereby enhancing your overall security posture.
Other options such as enabling advanced threat protection or implementing network security groups provide additional layers of security but do not directly address the specific issue of public access that may have led to the initial security alert. Allowing public access to storage accounts would actually be counterproductive, as it increases the vulnerability of your data storage infrastructure. Therefore, disallowing public access is the most effective policy definition to enhance security and prevent similar threats in the future.