C NOTE

wheech

My phone is full of malware. I've got the ROM at 4pda - it's russian main smartphones forum. So the chance they've modified firmware is very low i suppose. More about the malware:
1) i've got a tiny overlay button which appears on every screen except when screen is locked. it won't dissapear until i tap it. And then it opens some ad page. Not in browser but just as some app.  
2) When i open Google Play, it opens some paid apps like forex etc. Sometimes it's even downloads and installs and launches them without any permissions ask! And i don't have a root, so the hell how is it possible?!
3) Same as button but an overlay on the bottom of the screen
4) It launches the default browser on specific pages.  
5) and maybe it uses my phone for some ddos or bruteforce attacks, cause phone dies really quickly.  

So how did the viruses get into my phone system? I have noticed that the malware shows itself not directly after ROM reinstall but after a few cloud firmware updates installed. sorry for that english. i couldn't find russian umi support. i saw umigidi support employee in my phone's topic at 4pda but he hasn't been there in a while.