I am using a Windows 8.1 64Bit OS. A few days ago my antivirus AVAST detected a rootkit C:\Windows\System32\Drivers\Wdf45726.sys
Every time I delete this file manually or thru AVAST it comes back after reboot. Avast does not allow me to Quarantine this file. I am unable to rename this file as i get "Access Denied" error even in Safe Mode and Logged on as Administrator.
I have used Adaware and Malwarebytes which found some more potential Trojans etc which I was able to remove easily except this one.
I ran EMISoft Emergency Kit and it too detected this.