This is merely a partial copy of this article: http://nakedsecurity.sophos.com/2014/05/19/first-aid-for-android-how-to-unlock-your-ransomed-phone/ – for more detailed reference of what to do in safe mode and why use it, read that one. This gist is “to keep around if need arises”:
(Reported to work on Google devices and various Android Open Source Project, or AOSP, derivatives like CyanogenMod.)
- Press and hold the power button as you would to power down or reboot.
- A menu will pop up.
- Tap and hold the “Power off” option.
- If nothing happens try the same with “Reboot”.
- A dialog should appear offering you to reboot in Safe Mode.
(Reported to work on Samsung Galaxy S4.)
- Power down.
- Turn on and repeatedly tap the soft-button for “Menu.”
(Reported to work on Samsung Galaxy S3 and others)
- Power down.
- Turn on, then press and hold Volume Down (Galaxy S3 and others), Volume Up (HTC One and others), or Volume Down and Volume Up together (various Motorola devices) when the vendor’s logo appears.
If you have managed to select Safe Mode, you will see the text “Safe Mode” at the bottom left corner of the screen.
To get out of Safe Mode, try simply rebooting.
If that doesn’t work, try rebooting using one of the button-press options listed above, starting with the one you used to engage Safe Mode in the first place.