Study: Factory reset not effective

A study conducted by security software company Avast shows that Android’s stock factory reset feature does not clear all of the data from the device. The researchers say they are easily able to view users’ personal files using publicly available software even when it seems the factory reset is successful:

Although at first glance the phones appeared thoroughly erased, we quickly retrieved a lot of private data. In most cases, we got to the low-level analysis, which helped us recover SMS and chat messages.