Apps installing by themselves I have old android phone, which is working on 4.4 KitKat. Up to last week, phone is working very nice from last two years. But from last week, I saw some apps are installing by them selves. I didn't downloaded them.

Further I always keep my Android setting as "off" for installation of apps from unknown sources. But this do not work!! They are still automatically installing rapidly(their name are Uc news, superb cleaner, and many more). They are installing when I turn on my data connection. I used WiFi connection, so could not restrict background data of apps using settings. 
Further I had uninstall all apps which I had installed in last six months, but this does not do anything. I am not so much familiar with computers and android. I want simple way to secure my phone. What to do please help me.
Your device may be infected, and this causes all these apps to be installed alone. I advice you to find a proper rom and reflash your device.