In Pictures: Customise your Android device with Cy...
Better security to root access
In CM7, root access was left open by default, but the CyanogenMod team decided it was time to lock things down with CM9 for better security. They felt there is a limited need by most users for root access to their devices, but still wanted to make turning it on available. So now a fresh install of CM9 will present you with four options for enabling root: Disabled, Enabled for ADB Only, Enabled for Apps only, or Enabled for both. (ADB stands for Android Debug Bridge, and it provides access to an Android device’s file system through a terminal interface.)
In Pictures: Customise your Android device with CyanogenMod 9