How to Block Pre-Installed Auto App Installer Malware? I dont know which pre-installed app is auto installing new apps.
But I think its com.android.system.service (also on few other phones: http://en.miui.com/thread-459132-1-1.html)
Firewall is not supported for this old OS phone (I think its gingerbread)
Also No root available for my phone. I also tried all auto rooting apps for android and PC.
Because its old Android OS, there is no option to disable any pre-installed app.
I think antivirus is deleting only few harmful apps which are downloaded by pre-installed malware app.


The malware app is downloading apps to a hidden folder (.sysAndroid/Download) in sd card, I have no threat to my internal memory because its full.

How to make a folder on sd card unwriteable without root or with any trick?
like making a fake folder with same name to stop virus app from saving new apps in folder again(.sysAndroid or Download)

Or any other method?
First, you could make that folder "un-writeable" easily without rooting. As it's located on the SD card, and you're on a pre-Kitkat device, any app should have full access there:


Get yourself a file manager
navigate to /sdcard/.sysAndroid
delete the Download folder
create a new text file called Download, and make it read-only


Now, that malware app can no longer create the directory, as a file with the same name is in that place.

For other measures, we'd need more details (and I could update my answer then):


go to Settings › About Phone and check what Android version is running on the device
find out which app is installing the unwanted apps. I didn't test it with pre-Icecream devices, but my tool Adebar should be capable of that¹: Among other things (which require at least Kitkat), it creates a list of apps installed on the device, grouped by their installer (see here for an example: as you will notice, the package name of the installer is noted along). If your Android version indeed is older than 4, you most likely will not be able to "kill" that app, but other measures might be known.




¹ Adebar will require adb installed on your computer, and Bash being available – so a Linux machine is best suited for that. But it's reported to work well on a Mac, and even on a Windows machine running Cygwin.