There was an app, App Shield (since removed from the Android market, here's a description on Android Zoom) with a unique feature that allowed a non-rooted Android user to remove permissions from other apps. It was designed to allow people to deny specific permissions when those permissions were for features they weren't planning to use.
My question is: What specific security risks (if any) does/did App Shield pose?
I'm looking for specific facts and references to what App Shield does, from people with specific expertise of Android security, how Android apps function, and App Shield's specific features and functionality. The only information I could find in my own research was of uncertain reliability or based mostly on opinion.
Any facts on the specific reasons given when the app was pulled will be useful background, but the question is about what specific security risks there are with that app.
Please focus specifically on App Shield. I'm aware that:
- ...a hypopthetical app that modified another app could write in malware features. I'm not asking about a hypothetical app, I'm asking specifically about App Shield
- ...App Shield's functionality is controversial and touches on a debate about the merits of the Android permissions system and what Android apps should and shouldn't do. I'm not interested in that subjective debate and controversy. I'm asking about specific risks in App Shield.
- ...there are always security risks with apps not on the market. I know about this, I'm asking specifically about the original App Shield app.
- ...an App Shield user could break the apps they modify or cause them to crash by removing a permission that that the app then tries to use. That's unrelated, I'm asking about security risks.
My original wording of this question went into a bit more detail on why I was interested, and it has a very rough summary of my research and efforts to establish the story of what happened with App Shield. Apparently that sort of thing is too subjective. But check the edit if you want more context.
A correct answer might look like this:
"App Shield is unsafe because apps it repackages are
( placed outside of X path / lose Y protection / changed in a subtle way that shouldn't be described on a public site ) leaving them vulnerable to being modified by
( other apps that have Z permission / some other type of activity ). The malware-modified app will be able to
( gain any permission / use only its existing permissions but in malicious ways / do anything ). So it
( is / isn't ) possible to use App Shield safely
( but only if ... )"
"The original code of App Shield was largely safe because
..., but it could become dangerous if you
... and I
( would / wouldn't ) normally advise against it because
.... It is possible to use it safely if
.... Apps like App Shield are forbidden on the market because modifying other apps is against the Android Developer terms, and apps like App Shield could be used to turn other apps into malware,
( but / and ) the original App Shield code is largely