Android-How prevent manual installation of android application

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http://stackoverflow.com – I have an application A that launches an intent to install application B(which is present in app A's data folder). Once application B is installed, file managers like ASTRO can backup Application B's apk file. So I want to prevent the user from manually installing it(say if he clicks on the backup apk file of Application B it should not install). Is there a way to disable manual installation...? (HowTos)