The data that you save your phone or your SD card can be easily recovered, even after you delete it or factory reset the device using some very simple tools available on the internet for all, such Recover my Files, etc.
The files on you device that you delete aren't actually deleted from your device, since permanently deleting might cause errors and therefore, when you delete a file, the memory block that it was using is just marked as ready to be overwritten.
When you add a new file to your device again, the memory block marked 'ready to be overwritten' is overwritten by the new data, and after that the old data is permanently gone. But until then, any ofit can be recovered, and if it gets in the wrong hands, the person can use the cookies and other data to hack every account that you used on that device.
There are a lot of private and compromising photos on almost every device, and you might not want some stranger to get their hands on such stuff, sometimes even the phone companies recover this data if you give them the device for repair.
SO, what should you do to permanently delete your data before selling off you phone?
The steps are pretty simple,
- Format the device, and then fill it with useless data such as some funny video, or even some pdf files or songs(new owner might like songs).
- There is an option to encrypt all the data on device, use it to encrypt all the data before formatting and then format the device, none of the data can be accessed later since it e=was encrypted.
That's about it, for any queries, ask me in the comment box.
also see, Stagefright vulnerability in android http://goo.gl/ezeZMt
