At the end of 2017 I decided to reset my Android tablet. I used it as an auxiliary on-field device. There was no important data on it, but it could do with a clear down, a fresh start. The factory reset is a very easy task on Android devices.
I ran the reset task, it restored my device to a clean state and everything looked fine. I spotted McAfee anti-virus on it and ran it just for fun. It updated itself, started the scanning process and alerted me of the threat. I had a Trojan virus on the factory reset device.