You can modify SE Android to monitor devices and improve security, but doing so requires rooting devices, so it isn't for everyone.
Security enhanced (SE) Android is based on SELinux,
Getting shell access is easy: Have users download SSHDroid, an Android app that allows you to access their devices from a computer using Secure Shell (SSH). Gaining root access may be a bit more complicated. You can either use the Android Debug Bridge (adb) command, which is part of the Android software developer's kit (SDK), or you can root the device to get full access. Taking this approach isn't for everyone because device vendors don't support rooting.
Running SE Android commands from the Android shell
Once you've obtained access to the Android device, run the getenforce command, which tells you which mode SE Android is currently operating in. In Android 4.2 and 4.3, SE Android runs in Permissive mode by default. In Android 4.4 and later, SE Android runs in Enforcing mode, which provides more protection than Permissive mode. Enforcing mode prevents malicious actions and logs application data to offer device protection, whereas Permissive mode only logs system calls; it doesn't block anything.
Before you switch a device to Enforcing mode, you need to see if SE Android is blocking apps and functions that you don't want to be blocked. Find out by typing dmesg | grep avc. The dmesg command shows you all events that the kernel has logged, and grep avc lets you see all system calls that SE Android has blocked.
Understanding SE Android denials
Unfortunately, it can be difficult to understand the messages that SE Android logs. All of the avc messages indicate an action that SE Android blocked, but the logs cannot tell you if it was a malicious action or an action that should normally have been allowed. Sometimes you won't be able to tell what is being blocked or why. If the log messages leave you confused, try switching the device to Enforcing mode and see what happens. This will block many functions on the device, but it will also let you see what functions will and won't work anymore.
To put a device in Enforcing mode, use the command
adb shell su 0 setenforce 1,
then reboot the device. Try some apps after the reboot and see which ones work. Taking
inventory will help you decide which apps and actions to re-enable. You will need to create rules
to enable those features. The easiest way to do that is to capture all the denial messages, store
them in a file and apply that file to the SE Android environment of a device with
audit2allow using the command
adb shell su 0 cat /proc/kmsg > denial.txt
Before continuing, look at the file and try to understand why the denial messages are coming in.
Once you're confident that you want to allow the system calls that had previously been denied, you
can use the command
out/target/product/<your-device-here>/root/sepolicy < denial.txt. This opens SE
Android for all system calls that were previously blocked.
This was first published in February 2014