Erasing mobile phone personal data before sale or disposal – October 2016

I read an interesting article in a newspaper many years ago about people selling their mobile phones to buyers on eBay, and the security risk people could potentially let the new owner of that phone gain if they can retrieve your personal data from it. Some of the types of information are photographs, contact address book, text messages, notes, calendar appointments, emails and even passwords that were used with the phone, apps and the web browser site passwords and history. Some buyers on eBay that performed a security test purchased 2nd hand phones from random online sellers, and they were able to recover the previous user’s personal information from their old phone’s memory.

Here is an article about the scale of the problem published in 2015:

To me, this is a relevant modern day security risk that I wanted to research a good answer to, and think of solutions that will protect personal data when devices change ownership. I’ve only ever sold one of my old phones after an upgrade, it was an Android Samsung Galaxy S4, and fortunately for me, it was encrypted before a factory reset was performed (I always used the encryption on it when I owned it) so that it was ready for the new user and no chance of my personal data being discovered by that person or an expert they may know to retrieve the data from it. Don’t think that it’s not going to affect you, it won’t have any impact on you or that it’s okay because I have nothing to hide. Personal data can be used against you by dishonest people in many ways, so don’t ever make it easy for them. Ignorance is not going to save you, if you don’t know how to protect yourself, you should learn. Would you leave the front door open to your house and let people steal paperwork from your filing cabinet?

It’s a current and future problem now that smartphones and tablets are the normal trend for people moving to pocket sized computers that are just as capable in function as their laptop and desktop. This applies to anyone who sells their old phone or tablet after upgrading to a new device, replacing a broken device, with the owner just carelessly throwing their broken or unwanted device into a bin which can be possibly retrieved by others later. The point I am trying to make is that you could be letting someone use information about you to their advantage and more than likely to your disadvantage if they manage it. This article I have written about it aims to have some methods on how to secure against such a data breach happening to you by preparing you for some methods of erasing the phone or tablet correctly before it goes out of your hands with another owner. The same applies to laptops, desktops and servers. You can’t trust that people won’t try and find old information on a system in these days of increasing fraud, cybercrime and financial banking attacks.

I found this article on how to securly wipe a phone before selling it that you should consider to read before making your plan on how you will secure the sale or disposal of your device when it’s no longer needed by you:

This article explains about the same data cleansing on tablets as well as phones, so it’s worth reading for some extra data safety ideas:

You can also read this article for proof on why on android phones, a factory reset is not good enough to secure against the last user’s data being uncovered: I would imagine this extends to other types of phone too such as blackberry and windows phones.

So with Android, it looks like the method is to fully encrypt the device and then factory reset it 😉 I would repeat it a few times myself as it is possible to use equipment that can detect tiny particle traces of data before they were changed to the current content. Although these machines are expensive to buy, it doesn’t stop anyone using a service to get data from someone else’s device when they pretend it to be their own. The more reliant we get with mobile devices organising the way we work and live, we must also be aware of risks involved by not securing the information we store in them.

Magnetic disk certainly allows overwritten disks to be recovered forensically, which is why you see computer wiping tools such as KillDisk Pro from the Active Boot Disk Suite using wipe algorithms like the Gutmann 35 pass wipe to prevent those methods of getting poorly erased data back. It takes about 72 hours to run the wipe from beginning to end. You may think that it’s overkill or paranoia to use such a strong erasing method, but I have used the Guttman method myself at work to erase customer’s credit card data from decommissioned servers at banks in London before they were disposed of or sold to other companies for re-use. Because the software wiped the drives, the servers were sellable as complete working units because the hard drives were not destroyed, just the data on them was erased for good, and made the bank quick money.

Apple wipe options are very good apparently, but I still don’t trust that there are no backdoor abilities for Apple to recover wiped handsets, that is unless I know for sure this isn’t the case. Apple are very sensitive about their security in general, to the point that they will defend it strongly, even if law authorities need to break privacy.

John Mcafee recently hacked an iPhone login PIN number in a famous USA murder case. The phone they hacked into belonged to a dead suspect, so they were not around to ask them for their PIN and they were looking for clues about the murder from his iPhone. John famously got around the login for the FBI since Apple would not help them circumvent the pin login to get access to the phone.

I am suspecting that reversing a phone wipe on an Apple iPhone or iPad device is possible, if only for a few Apple experts within Apple that know how to decrypt the old data before it was factory erased. I honestly don’t know how safe the iPhone wipe is, and only Apple really know this. I do have a suggestion to make it a lot more secure.

First remove the phone from the icloud and turn off “Find my phone” (Settings, iCloud, Find my phone, switch the slider off and enter your Apple ID password to remove it) or it will be unuseable to a future buyer that you might want to sell it to. You can still keep your personal icloud data and get to it from a computer at web address – and even transfer it to an upgraded iphone by using the same apple ID on the new device.

Then to wipe an iphone, goto settings, General, Reset, Erase All Content and Settings. Enter device password or pin if there is one. Confirm erase and watch it wipe itself, it takes about 5 to 10 minutes depending on the model (newer is quicker) and the capacity of storage on that iPhone.

Then here’s the security kicker to prevent even Apple performing forensics, the best way of making sure it’s impossible to get wiped data back, is to fill up the phone’s internal memory (iPhones don’t have external memory cards yet but Blackberry, Windows and Android can depending on the model) with junk data after a factory reset of the phone is done. If external memory cards are being used with an old handset, you should either remove it before it changes hands, or plug the media card into a caddy that connects it to the computer so that you can use a secure erase program to wipe the data. When complete, the media card can go back into the phone.

To achieve this internal phone wipe, create a large file containing completely random data. Based on the phone’s internal memory capacity, you need to make the file exactly big enough to completely fill the entire free space on the phone. Upload that file to the phone’s free space, then wipe it again in settings (factory reset) for good measure. I would repeat this process several times over to make sure the data cannot be recovered using expensive recovery hardware. I am sure that it wouldn’t be too difficult for anyone to code a program to wipe a phone securly, as paid for products that do this can be expensive for businesses, I bet someone somewhere has written such a mobile phone sanitising program as freeware to automate the process. If I can’t find such a program, I can write it.

When it comes to your old phone or tablet, does anyone still need it?If you don’t want to sell it on, give it away to someone and don’t want to use it anymore yourself, you can go for a complete hardware destruction by using three fun methods that spring to my mind:

1) You can buy an electro magnetic degausser machine from here: – Just as an example shop.
The ones they sell there are big and expensive, you might be better off looking for a smaller version that is just for personal low volume use. I used to have one that erased audio tapes before CD’s were used for music. I could wipe a whole tape in 3 seconds with it. As for destroying a mobile phone with a degausser, it will need to be strong enough magnetically that it damages the memory chips in the phone beyond repair or recovery. It shouldn’t take much to wipe the memory chips of a mobile using a powerful industrial sized machine.

The NHS in the UK drill holes through their old hard drives, which they think secures them before disposal, but they should be using degausser devices as the site to buy them correctly states, that you can still get data of a drive with a hole drilled through it.

Degaussers are used to this day by very secure departments of government who handle sensitive information. Examples are the NSA, FBI, CIA, MI5, SIS, etc. It’s a great gadget to have and for peace of mind, it’s worth the investment in one. The phone will never work again if you use this method on it correctly. A high strength electricity amplifying the magnetism and this coupled with long enough exposure to the electromagnet will render the device useless. It will internally fry the internal circuit board’s attached microchips inside the phone, which is including the memory chips that you want to make sure are not recoverable by anyone else. It will also write off any other electronic components in the phone such as camera and flash, memory cards if inserted, screen LCD display and touch sensors, speakers, etc. Enough electrical current strength and longer the time that phone is exposed to it, the more secure the degauss method will be in making the memory useless to any modern forensic data recovery techniques. EMP (Electromagnetic Pulse) weapons can cause a similar internal destruction of the microchips in the phone, but these devices are illegal in most countries due to their ability to destroy any electronic devices they are in range of. They are used by the military to take out an enemy’s communication, so access to these devices are legally restricted, although the devices do exist to buy on the internet.

2) I find there’s nothing more satisfying than a good old fashioned hammer, be it a normal workmans hammer, a club hammer or a sledge hammer! It can crush a phone into dust if hit against a tough surface hard enough and the strikes to the phone are repeated enough until the chips in the phone are crushed to dust.

3) Use an incinerator. It would melt the phone at metal and glass melting temperatures leaving nothing physically left to recover data from. The phone would be turned into ashes at best using that. No forensic or cryptography expert would ever be able to recover data from a pile of ashes 😉

Good luck, and keep your personal information safe folks! Roasty.

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