A free program for Android, by GTTM Team.

If you are concerned about your privacy and security, then you should definitely use the App Locker Master. It is a simple, easy-to-use, and very effective app. With it, you can lock your applications and hide them from the public. You can also lock your gallery, messages, and social apps with a simple pattern. This is an excellent tool to help you protect your privacy. It also works with the front camera. If someone tries to open a locked application with the wrong password, it will show an image of the intruder from the front camera.

You can also set a time for the lock to be activated after the screen is turned off. This makes it easier to use.