Ever sold your old smartphone when you upgraded to a new model? Then you might have handed over a lot more personal information than you thought...

We use our phones, which are essentially tiny computers, for pretty much everything these days. They serve as our communication tools, our cameras, we can even do our mobile banking on them, and that means that a whole heap of personal information is stored on that little device in your pocket. 

However, if you've ever sold your old phone after an upgrade or flogged it on eBay for a bit of spare cash, then you might have given away a whole load of that information to whoever bought it from you, even if you did your best to wipe it clean. The folks at avast! offer anti-virus and software for your phone that protects your data in the case of it getting stolen, and they decided to do a little experiment. They bought 20 used phones off eBay, and managed to find a whole load of personal data on them. 

The findings were particularly worrying for Android users, as with the help of "simple and easily available recovery software", they got back a staggering amount of data including more than 40,000 photos, which included snaps of the previous owner's children, as well as 750 pictures of females in various stages of undress and 250 shots of the manhood of the person who last owned the phone, not to mention location data and a whole bunch of other personal information.

Apart from letting us know that people really, really like to send each other nude photos of one another (yes, that means you), the data also shows that we're not as well protected as we thought, as the phones were all supposed to have had any personal info already cleared off them. Avast! were able to find out who the previous owners of four of the phones were, and although the data was from American phones, the infographic produced is still pretty interesting. You can click the picture for a larger image, if needed.

The reason that Android users are particularly vulnerable is that hitting the factory reset, which most people do to clear their data, is not enough as the data is not encrypted. On the other hand, iPhones run encryption as standard, so when you hit factory reset, the encryption key is also wiped making it much more difficult to recover anything from the phone.

Via Avast.com and UsVsTh3m. Main pic via Sebastiaan ter Burg