Starting with Android 4.3, Security-Enhanced Linux (SELinux) is supported by the Android security model. Android security is based on discretionary access control, which means applications can ask for permissions, and users can grant or deny those permissions. Hence, malware can create havoc on the phones by gaining permissions. Android uses SELinux to enforce mandatory access control that ensures applications work in isolated environments; this includes applications running as root or superuser. Hence, even if a user installs a malicious app, the malware cannot easily access the OS and corrupt the device. SELinux is used to enforce Mandatory Access Control (MAC) over all of the processes, including the ones running with root privileges. SELinux operates on the principle of default denial. Anything that isn't explicitly allowed is denied. SELinux can operate in one of two global modes: permissive mode, in which permission denials are logged but not enforced, and enforcing mode, in which denials are both logged and enforced. As per Google's documentation, in the Android 5.0 Lollipop release, Android moves to full enforcement of SELinux. This builds upon the permissive release of 4.3 and the partial enforcement of 4.4. In short, Android is shifting from enforcement on a limited set of crucial domains (installd, netd, vold, and zygote) to everything (more than 60 domains).