I will be passing on my company phone for someone else to use for couple of weeks, and I am having some privacy concerns about it. I have already transferred all images/videos from the phone's ext SD card, but now I am worried of how I can securely erase the data. I don't wanna buy a new SD card just for this, so I was wondering if there is any way to safely erase/destroy those data.
For starters, I got my self 'secure file deletion' from play store, which allows to wipe off selected data off the phone memory and the external card. Which I did. Images/videos are stored under:
But after wiping those off, I realised that not all image/video data is cleaned off. The OS also stores thumbnails for those media. Surprisingly, those are stored in phone memory and location can't be changed:
In there, there are .JPGs (thumbnails) and a strange '.thumbdataXXXX' file. So, I use 'secure file deletion' to remove those as well. Funny thing is that even after erasing those, I can still see the thumbnails of the corresponding video/image (but when I select it, it says 'file not found' - which is expected, because its already been wiped). Nevertheless, my guess is that the thumbnails of those videos/images are also cached elsewhere. But where?
My question is - is that all there is to it? Is the OS storing any more related data in regard to images/videos that I need to wipe? Are those actions I have taken enough to give me peace of mind that my media are safely wiped off beyond recovery?
I found that the secure deletion apps are very few, most of them require root and most even don't work properly (e.g. files reappearing after wipe etc). There are some good ones like 'ishredder 3 pro' and 'clean master' that offer secure wipe options - but only for wiping off entire phone/card memory - which is not what I want here. Any more suggestions?
The phone is a non-rooted Samsung with 4.1.2 Android OS on it. I don't wanna root the phone and I don't want to wipe entire ext card - so any suggestions, please bear that in mind.
Makes me wondering why there isn't any build-in function to the OS for secure deletion of files? Sure it would be slower and not everyone would applaud it, but it could be enabled on demand e.g. via Developer Options...