Antivirus

Be it a low-end smartphone or the latest, having an antivirus is essential as it is on a computer, android viruses are increasing and so we should be aware of them and how to take care. They can ruin your phone or steal your passwords, and do many other things. I have found a files called "keylogger.txt". This was a key logger i.e it recorded all his keyboard presses (passwords mainly) and stored them and sent them somewhere. So be it a free one or paid one or a cracked version :-p get an antivirus and protect your phone.

Some recommendations:
Bitdefender
Kaspersky
AVG
Avast
360 Security
Avira
McAfee

As always, Better safe than sorry.