@muhit23 I have never had issues downloading apps from my dropbox app and installing it on my phone. If your carrier restricts you from outside of the market, that might be the issue.
Unless the app that you download outside of the market is from a reputable source like the Amazon App Store or some others that the developers agreed to market their apps on, you don't really know whoever uploaded the app didn't alter it for malicious reason.
So, the app from the market don't have any permission used for malware but the same app you got off the Internet might.
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