Poke a Used and Reset Android Phone: it’ll Spill its Guts

| Particle Debris

If you're reading this, it's likely you're a fan of Apple and probably don't have an Android smartphone. But just in case you have a friend or family member who does, show them this next article that I link to below. A security company, Avast, purchased 20 different smartphones on eBay, phones that the owners presumably thought they'd wiped clean, and used a data recovery tool.

What they found will alarm you.

In contrast, iPhones use a hardware encryption, so when the encryption key is destroyed on a reset, the data is very hard to recover. Not so for Android phones apparently. Here's the story: "Hard Proof That Wiping Your Phone Doesn't Actually Delete Everything."

So ... I'll never forget the time, years ago, in Aspen when I asked a ski tech to tune 0/0 degree edges on my K2 skies. His response was "scary, man, scary." That's how I felt about Android smartphone security after I read that story.

Apple does everything it can to tell the story about how the company is using the best available technology to protect its customers. But perhaps people ignore that fact because they just don't want to hear about it. The article above explains the awful discovery in very clear terms, so there's really no excuse for feeling overwhelmed by the technology described there.

Another reason people may ignore the differences between Apple's iPhone and other smartphones is because some writers go out of their way to dramatize every little problem with iPhones and readers are, thereby, unable to put into perspective the relative risks. While there are occasional iOS lapses, not every bug gets a weaponized response and results in a pandemic of compromises.

The recovery of "40,000 photos (including 1,500 family photos with children and 250 selfies of someone's "manhood"), 750 emails, 250 contacts with names and addresses and even files such as a loan application..." should give us pause about which company we want to bet our technical future on.

Next: Tech News Debris for the Week of July 7

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Link to Case #2 about Cortana appears to be broke.


Re the problem with smart people.  I have come to notice that some people who have achieved great expertise and success in one field tend to act and think is if they are experts in all fields.  You see this everywhere.  Physicists who freely and publicly weigh in with their opinions about climate science, some of whom end up bolstering climate deniers.  Electoral campaign wunderkids who then fancy themselves policy experts once their candidate gets to the oval office.  Or my particular favorite example,  applied mathematicians who believe themselves to be crack economists and run securities investment models that assume housing prices will rise forever. 

God spare us from people so smart that they CAN argue any position convincingly, but not smart enough to realize that they can argue ANY position convincingly.

John Martellaro

nolatransplant:  Thanks.  The link is fixed.

Lee Dronick

Sounds like an opportunity for a programmer to write an app that would scrub the device, would that be possible?



The problem is with Flash memory. It’s not the same as magnetic platter memory, where you can write 0’s and 1’s until the data is “scrubbed”. First, there’s the technical limitation to the writes that flash can have, around 10,000 or so. Then there’s the mechanism that was implemented to prolong the life of that very same Flash memory. The controller doesn’t write to the same cells, it uses the least used cells first to write to, that way the memory degrades at the same rate through out the memory array, and the way each manufacturer implemented this goal is different. There is no reliable way to just secure erase one portion of flash memory.

This isn’t just an Android Phones problem, this is a thumb drives, SSDs, and yes, the iPhone too, problem.


And John, decrypting encrypted data isn’t that hard. Maybe you’ve heard, but encryptions that were thought to be near unbreakable just 5 years ago are routinely broken within hours now with current decrypting tools.


Oh, and of course Edward Snowden did reveal that every commercial encryption scheme used in the US has a built in vulnerability that allows the NSA to more easily circumvent the encryption used, not that people who would buy a few thousand old iPhones to get personal data would even be aware of Edward Snowden….



I so wish I could just edit posts…

Lee Dronick

Thanks Daemon.

Lee Dronick

  It was recommended by Google that all users enable encryption on their devices before applying a factory reset to ensure files cannot be accessed. This feature, said Google, has been available for three years, although it is not enabled by default, which could leave less tech-savvy users open to attack.

Apple has had built-in encryption for its hardware and firmware since the release of the iPhone 3GS. The hardware encryption is permanently enabled and users cannot turn it off.




I understand your post on the difference between magnetic platter memory and flash memory, and the difficulty in erasing just one portion of flash memory.  But, I would think it would be simple to write an app that you could install before a factory reset that basically fills up all available free flash memory space (other than OS) with garbage data, and then when the factory reset occurs all previous data would be gone.  Or, for goodness sake, as part of the factory reset it should wipe everything (other than OS) and THEN write garbage data to ALL available memory and then delete that.  Can’t be that hard to do.


I recently found an android smartphone at the bottom of a river. The face was smashed as well. Once it dried out, I was able to fire it up. It was locked with a PIN and I could not access it.
Of course, I could get to nearly all of the data (pictures included) that were stored on the micro SD card. There were no naked selfies or anything, but I did learn a lot about the owner.. including name, phone, email and physical address of the former owner.
Locked didn’t matter at all.
“Destroyed” (Smashed + Riverbound) also didn’t matter.



The problem is that all writes and reads go through the microcontroller, and the microcontrollers are by patent necessity different from each manufacturer. While what you suggest could be possible, it’s also just as likely that any attempt to write “garbage” to the drive would be ignored by one controller, another controller might only write garbage to 90% of the drive that had nothing on it to begin with, and a third might write the garbage over everything but protected areas. Desktop SSDs have a newish feature called “trim” that first requires it to be enabled by the operating system, and then as part of garbage cleaning cycle is supposed to 0 out the cells that held deleted files. One of the interesting side issues is that you can’t just enable trim, it has to be there from the time the OS was installed. The SSD works perfectly fine without trim, I doubt anyone would even notice it not enabled. The files still “delete” in that they disappear and the associated cells are shown as available for other files.

The reason why it’s not as simple as just writing a bunch of garbage to the entire disk Ron, is because you have no way of controlling what is and isn’t written to the disk, it’s all hidden from you, by the microcontroller.

Keep in mind, Intel sells 40, 60, 80 and 120 GB drives that are identical to each other when you look at the internal pcb, all they did was disable certain areas of the flash memory. The memory could have failed QC for the larger sizes, the memory could be perfectly fine. Intel might be using the extra 80 GB of disabled memory as backup for the 40 GB of enabled memory so that their drive has a lower failure rate than competitors. You could write 80 GBs worth of garbage to a 40GB drive and never once write over a single bit on the 40 GB drive.

The issue Ron, is that you don’t have access to the internal structure. On normal HDDs we have the low level access past the microcontroller to access the exact spot on the platter that the data was written to.


Excellent points.  Appreciate the technical stuff, daemon.  Apple has ensured that trim is included in the OS for some time now.  However you do have to ensure that you use the trim feature if you so desire.  The only way to do this is to restart your system from a backup system and then ‘repair’ you flash drive with apple Disk Utility.  As a last step it notes “trimming unused blocks”.  Works on any Apple OS flash drives (but not iOS of course).  Talk about easy - right!?  Drives are not trimmed automatically.  I stand to be corrected if there is an easier way.


Thanks for the education, daemon.  I had no idea that something which seems so easy would actually be that difficult.

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