Malware automatically installing unless I disable the play store So I have been working on my brother's Elite 6.0l+ Sky device. This poor thing has been struck by the xhelper virus which auto installs firedoor, firemyn and an app that likes to hide itself by appearing to be settings. 

I have been chasing this malwares source for a couple of weeks and through a ton of trial and error I've discovered that disabling the playstore seems to keep the malware from being reinstalled. However, if I re-enable the playstore so I can grab a game or check for app updates, the malware is immediately re-installed on the device. 

I have also discovered that the device itself is apparently known to come with pre-installed problems (SKY/x6069_trx_l601_sky/x6069_trx_l601_sky:6.0/MRA58K/1482897127:user/release-keys) but what I can't find any where is solutions! 

While disabling the playstore does keep the malware off the device, it's not exactly a perfect solution and if it's at all possible I want to remove this malicious pest at the roots so the phone will actually be totally functional. 

does anyone know how to deal with this? I'm tech savvy and completely comfortable in command prompt, and I'm not afraid to work with code if need be as long as I have instructions. 

Thank you in advance for any and all help!
regarding xHelper


unpack firmware247.com/sky-elite-6-0l-plus-firmware  
install VCOM preloader usb drivers  
install Mediatek SP Flash Tool  
load the scatter file, DESELECT all checkboxes (especially preloader)
switch off device completely  
flash boot, system (click Download only, Download, then connect usb-cable)  
flash cache, userdata (= factory reset if you wanna be 100% sure)


regarding OTA updater  

readback boot.img with SP Flash Tool, patch with Magisk Manager, flash magisk_patched.img into boot, root the device and disable the OTA updater from terminal or adb shell  

su
pm disable --user 0 com.adups.fota
pm disable --user 0 com.adups.fota.sysoper
pm disable --user 0 com.fw.upgrade.sysoper


after this, restore the original boot.img (unroot device) and uninstall Magisk Manager  

(Note: unlocking bootloader is most likely not required for this old device, SP Flash Tool can flash with locked bootloader. However, be aware unlocking bootloader will perform factory reset)