What is the MOST effective countermeasure to a malicious code attack against a mobile system?

 A sandbox is a security mechanism that isolates a potentially malicious code or application from the rest of the system, preventing it from accessing or modifying any sensitive data or resources1. A sandbox can be implemented at the operating system, application, or network level, and can provide a safe environment for testing, debugging, or executing untrusted code. A sandbox is the most effective countermeasure to a malicious code attack against a mobile system, as it can prevent the code from spreading, stealing, or destroying any information on the device. Change control, memory management, and PKI are not directly related to preventing or mitigating malicious code attacks on mobile systems. References: 1: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 8, page 507.