Apple iPhones sold as refurbished units may still contain lingering personal data from the previous customer, according to iPhone Atlas on Monday. Using a forensic toolkit, a detective was able to recover personal data that included e-mails, photos and even financial data. Techniques to perform low-level NAND permanent erase are scarce.

"As previously noted, performing a 'Restore' operation on the iPhone does not delete personal data from the device. Such information remains intact on the device after a restore, making the process unsuitable as a preparatory measure for iPhone resale or service. Apparently, Apple's refurbishing procedure also does not delete the personal data," the author said.

The situation was emphasized by Jonathan Zdziarski who has written a forensics manual for law enforcement officials. Currently, there is no widely available technique for erasing personal data on the iPhone. Mr. Zdziarski pointed out, "there are only a couple low-level methods to format the NAND and I'm not sharing at the moment."

While it's unlikely that the purchaser of your refurbished iPhone would seek out or have ready access to forensic tools to do this kind of data recovery, it's still good to know that personal data, despite your best efforts to erase it, could still be lingering in an iPhone that's returned to Apple in a warranty swap or sold to someone else.