This recent story appeared on Slashdot regarding various malware apps that had invaded the Android Market. Google quickly removed them (and I was not infected - I don't typically download apps), but I was curious - would a factory reset fix the problems that this malware caused (including rooting)? If so, why not?
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1+1 I found your question very interesting, I saw another article - androidpolice.com/2011/03/01/… mention that the malware apps are able to root the phone and even install a backdoor. What if it is able to change the image on the ROM in the phone, then performing a factory reset will be useless since the image is not the original and so the backdoor will still be there. Are there other solution to ensure that the image is not manipulated?– JackCommented Oct 31, 2012 at 1:32
2 Answers
For that/those particular piece(s) of malware, the answer is probably yes.
A factory reset does not completely undo rooting, especially with the more "invasive" methods used for a few hard-to-root devices. A simple/common exploit like the ones probably used in these rogue apps is less likely to allow them to persist.
A factory reset should also wipe out installed apps (including the malicious ones) or, if they're stored on the SD card or something, at least reduce them to uninstalled apps just sitting there -- and they can't do anything unless the user reinstalls them.
Factory resets generally leave the /system
partition intact, however, and any malware could theoretically have replaced system binaries with malicious versions or something along those lines. To be on the safe side you would want to re-flash your ROM and not just do a factory reset.
Adding to what Matthew Read stated, it most likely will not unroot, but on top of that, it will not stop the damage that it has already done with your contacts or data. I mean if it collected contact data and personal passwords ect. then you need to start changing passwords and all that good stuff.
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1Definitely agree, and understand this. I was just wondering if it would stop further damage (which Matthew Read answered pretty well). Basically, I didn't know if there was a way the trojan could install itself in such a way that a factory reset WOULDN'T remove it. (I don't know exactly how factory resets work - is it an uneditable image within the phone? Something else?)– JasCavCommented Mar 2, 2011 at 17:46