Securely delete files - Android

June 7, 2012 8:04 AM

How can I securely delete files on my Android phone? I want to be sure that deleted files can not be recovered, i.e., photos, email, email attachments, evernote notes, etc.

On my pc, I use eraser or Ccleaner to overwrite unused space. Will those tools work on the Android without screwing it up? I can do basic file management in *nix, but am not a guru, by any means.

posted by theora55 to technology (7 answers total)

What model phone do you have?
posted by procrastination at 8:37 AM on June 7, 2012

The only way to be absolutely 100% sure data is gone, is to completely obliterate the memory device.

Killdisc is good. it wipes, writes data in, and the wipes. Not sure if you can do that on a phone.
posted by couchdive at 8:52 AM on June 7, 2012

Most (all?) android phones keep lots of stuff on a microSD card. Keep your sensitive stuff there, and then take out and destroy the card if you need to.
posted by rockindata at 9:02 AM on June 7, 2012

It appears that it's quite difficult to securely delete data from a flash card. Probably the way to go is back it up, destroy it, and copy back the stuff you want to keep. But maybe there's an way to access those "spare cells" the thread I linked mentions, if you really know what you're doing.
posted by Estragon at 9:43 AM on June 7, 2012

couchdive: "The only way to be absolutely 100% sure data is gone, is to completely obliterate the memory device. "

A test was run on the claim that, with electron microscope imaging, data could be recovered (from hard drives) even after being overwritten. No data was recovered.

So, while you're technically correct (the only way to be sure is to do something you have real control over), it's possible to be sure to 5-sigma certainty.

Estragon: "It appears that it's quite difficult to securely delete data from a flash card. "

Hmm, seems to be a different case for memory cards. Maybe. However, a 99-cent Bic lighter is pretty effective at erasing data from them.
posted by IAmBroom at 10:04 AM on June 7, 2012

I think your best option on Android is to run encryption. There are a number of options available.
posted by zephyr_words at 10:18 AM on June 7, 2012

Memory card bits are either 1 or 0. Perhaps an electron microscope could find roughly how many times each bit has been flipped, but that doesn't tell enough.

Just delete everything you can, then copy in some movies in to fill up the whole memory space. Then some MP3s, then some text files of "ha ha ha you found me" for those last 100 bytes or so, get it down to zero bytes free, then delete them all. Then you could copy those type files back in in reverse order, then delete them again. That will be more than enough.

If anyone dares to spend a million dollars to recover the phone memory, they'll find "Plan 9 From Outer Space" and "It's Friday, Friday", and "ha ha ha you found me".
posted by caclwmr4 at 1:20 PM on June 7, 2012