How to Safely Prepare Your Smartphone to Sell

Published on July 18, 2014

When it comes time to sell or donate an older smartphone of yours, it is critical that you wipe all of your data off of it. The common practice is to put your phone through a "factory reset."

However, a factory reset really doesn't wipe your phone as clean as you may believe. Here's what you need to know to clear your phone of all personal data before you sell.

A "Factory Reset" Does NOT Eliminate All Personal Data

In a recent blog in Lifehacker, security researchers were able to uncover a substantial amount of data from phones that were "wiped" in this way.

In fact, Security software developer Avast!, using very basic techniques, found a treasure trove of information in 20 smartphones that were all "wiped" with the built-in factory reset option. Plenty of the information uncovered was personal, including:

  • More than 40,000 photos, including: 1,500 family photos (with children), 750 photos of women in "states of undress", and 250 selfies of "the previous owner's manhood."
  • More than 1,000 Google searches
  • More than 750 emails and text messages
  • More than 250 contact names and email addresses
  • 4 previous owners' identities
  • One completed loan application

We're certain this is information you would prefer to keep out of the hands of a stranger. Ensure this by cleaning out your information properly.

How to Properly Secure Your Phone to Sell

Now that we know that wiping your phone using "factory reset" doesn't do a complete job, what should you do? Here are some precautions you should take.

1. Remove your SIM card

Most data you store on your phone is held on internal storage or a micro SD card, but is is still possible for contacts or call logs to be stored on your SIM card. Remove this card before reselling.

2. Remove your micro SD card

Similarly to a SIM card, the SD card holds information that should remain personal. Remove this card before reselling. If you cannot remove it, proceed to #3.

3. Erase and format your micro SD card

In the event that you must include your micro SD card with your phone, make sure you erase it directly. This is usually done through the Settings on your phone. You can also do this through a PC, but it is possible that it can get formatted with the wrong file system for your phone. To keep things simple, do try and keep your SD card if at all possible.

4a. Securely wipe your phone's internal storage (iOS)

iOS users have a relatively simple job when it comes to wiping internal storage safely, as there are built-in options for this specific function.

Head to: Settings > General > Reset > Erase all Content and Settings

For any iPhone generation 3GS and later (and all iPads/iPod Touch 3rd generation and later) this process will be very fast, and very secure. For older devices, the process will take quite a bit longer. Either way, it will give your devices a nice secure wipe.

4b. Securely wipe your phone's internal storage (Android)

Android phones take a little extra work to wipe clean. Unlike the iPhone, Android encryption isn't done on a hardware level, so you'll have to enable this yourself in Settings. It will take some time and you will need to enter a specific PIN when you boot up your phone (which is NOT the same PIN as your lock screen PIN). (Note that this process can decrease some performance quality and that the process cannot be reversed, so make sure you're prepared to take the jump/sell your phone.)

Now that you've encrypted your phone, you can do one of two things to wipe your phone. You can now use the factory reset optionĀ (as your phone has been encrypted for further protection), usually located underneath something like "Backup & Reset."

5. Vet your buyer

Before you sell your phone, make sure your phone is going to a legitimate buyer or company. Additionally, make sure you've deactivated your phone with your carrier before handing it off.

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