apupdate downloading apk files on its own, please help

My android acting weird lately, it creates folder apupdate in sdcard directory and download unknown apk on its own, an envelope icon appear on the notification bar every time the download is finished. The apk files and notification text is using chinese text.

Is there someone with the similar problem? and know how to fix it?
How to see which application download the apk files?
Is there a way to block apupdate folder so it become unusable?

Tried using antivirus and delete the folder but it doesn't stop.. Please help and sorry if my english confusing.

 

Thank you, I will update my status after trying above method.

 

My phone back to normal, thank you. This thread can be closed