If you are about to turn in or hand down your old smartphone, you do a factory reset and everything is wiped clean, right? Well, no.
Antivirus firm Avast probed several Android phones that had been factory reset and managed to recover more than 40,000 photographs, the identities of four previous owners, one completed loan application, more than 250 contact names and email addresses, more than 750 emails and text messages, and more than 1,000 Google searches.
Like on PCs, the mobile OS deletes the corresponding pointers in the file table and marks the space occupied by the file as free. Eventually, the file is expected to be overwritten, but until it is, the file is still present and thus recoverable.