Android Factory Reset Does Not Erase Data, Warn Researchers

Mobile device owners have once again been reminded that it is often possible to recover personal information from a used smartphone or tablet, even after they went through a ‘factory reset’.

Ken Munro from Pen Test Partners told the BBC that this function doesn’t really delete data – just hides it from the system. The problem is especially acute on Android, due to its open nature.

Munro pointed out Tesco’s budget-friendly Hudl tablet as an example of a device on which previous owner data was easily recoverable due to a hardware flaw. To prove his point, he bought ten second-hand tablets on eBay and was able to recover personal data including Wi-Fi keys, cookies and browsing history.

In July, security vendor Avast published results of a similar experiment, in which it was able to extract hundreds of old photos, texts, emails, contact book entries and even a complete loan application from just 20 used handsets.

Digital ghosts

Munro explained that the ‘factory reset’ function often just deletes the index of files, with pictures, videos and documents still present in the device’s memory. Those can then be recovered using specialised software, which can be found online for free. The issue is made worse by hardware design and firmware of some processors, including the quad-core Rockchip that sits at the heart of Hudl.

“Customers should always ensure all personal information is removed prior to giving away or selling any mobile device. To guarantee this, customers should use a data wipe program,” said a spokesman for Tesco. We can add that encryption offers another way to make sure that deleted information is gone forever.

Researchers at Avast previously got their hands on more than 750 emails and text messages, more than 250 contact details, at least 1,000 Google search queries, 1,500 photos of children and 750 photos of women “in various stages of undress” – all from just 20 Android smartphones.

Avast said it was entirely possible to establish the identity of up to four previous device owners using simple, off-the-shelf data recovery solutions.

Meanwhile, Digital forensics firm Stroz Freidberg has just released a free tool that claims to protect consumers and businesses from an iOS backdoor that could allow an attacker to access personal data on iPhones and iPads by exploiting ‘pairing records’ – a mechanism that enables iPhones and iPads to safely communicate with a PC.

Some advice on how to permanently delete mobile device data is included on the government-affiliated Get Safe Online website.

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