ACME Corporation employees access critical business web applications through CyberArk Identity.

 To mitigate the risk of unauthorized access attempts from a specific IP range, the best practice is to block that range from accessing the CyberArk Identity portal. This can be done by logging into the CyberArk Identity Admin portal and specifying the IP range to be blocked. By doing so, any traffic originating from this range will be denied access, thus reducing the vulnerability and potential for unauthorized access.

References: The information aligns with the best practices for securing access as outlined in the CyberArk documentation, which suggests defining challenge rules for user-added applications or based on the application URL, application domain, or user domain (email) to restrict access1. Additionally, it is consistent with the security guidelines provided by CyberArk, which include implementing measures to contain attacks and prevent unauthorized access2.