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Recently purchased a Oneplus One second hand from eBay. It was factory reset by previous owner, and it has since been factory reset by me a couple of times.

I have setup Google Photo's today and it's pulled in all my photo's like it should. However, it has also resurfaced all the previous owners photos and is currently backing them up to my Google Photos account!

When i look at the info on the images, it seems it's dragged them in from 'storage/emulated/0'

I wouldn't normally be bothered by something like this but these photo's contain enough information for some serious fraud/identity theft! I have pictures of addresses, passports, credit cards, tax bills ....

How is this possible? Surely a factory reset should wipe all data?

For clarity, the phone is running stock Android 5, but is rooted (supersu) and running TWRP (both installed by previous owner).

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storage/emulated/0 is what often is referred to as "internal SD card". A factory-reset leaves that untouched – unless it has such an option and you select it (e.g. recovery offers that).

Which means, you have to explicitly clear that storage – or all files stored there remain there. Which obviously was the case with your device: neither the previous owner nor you thought to delete the card. If you "explore" it (e.g. using a file manager app, or by connecting the device via using an USB cable) you will most likely find many other files from the previous owner still existing there: data apps have stored, photos, screenshots and more.

If you want to erase contents of the internal or external SD card, you fine the corresponding "buttons" in Settings › Storage.

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A factory reset deletes the files on your internal memory, but does not secure delete them - or delete anything on your internal SD card.

When you press "Factory reset", it quick formats /data/ and /cache/. If you select "Also erase the SD card", then the internal SD card will be erased too.

If they can still be found with Google Photos after selecting the option to erase the SD card during a factory reset, try going to Settings > Storage and then select "Erase SD card".

If you really want to fully erase everything, use a secure delete program (it will fill the internal memory with a file filled with 0's and then delete the file), so you can't recover deleted files.

  • It's not the "traces of deleted files". It's the "internal SD card" not being erased at all when performing a factory reset unless such an option is available and selected (neither the external). Google Photos may do many things, but it for sure doesn't undelete erased files. – Izzy Oct 16 '18 at 15:53
  • Surely this is a big security risk? with the type's of data people are keeping on their phone's why wouldn't the factory reset option (that to the layman wipes 'all' data) wipe everything in a secure fashion? Is this an older Android thing, or is this still the case in newer versions? – Barry Jarvis Oct 16 '18 at 15:57
  • @BarryJarvis it was not my design decision. I was as confused as you when I found that out first. But thinking about it, it makes some sense: if you have trouble with your device you cannot solve yourself, service hotlines of the manufacturer always recommend you a factory-reset before asking you to send in the device. Sometimes that solves the issue. Data on the card shouldn't affect those issues, so they are left untouched in such cases; if you want to erase them, there's an option to do so in the storage settings (will update my answer with that). – Izzy Oct 16 '18 at 16:00
  • @Izzy I updated my answer to descibe how to format the internal SD card, instead of the internal storage. – Zackary Oct 16 '18 at 16:01
  • @Izzy - no questioning your answer at all... to me it just seems a blatant security issue, given the data people are storing on these devices. – Barry Jarvis Oct 16 '18 at 16:05

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