The powers that be commented re detection
It's not just us. With the latest campaigns, the authors make sure majority of AV vendors do not detect when they release so that they can maximize victims/infections.
One of our users got infected as well.
It is important to notice that the HELP_DECRYPT files are a symptom of the infection/encryption and not the cause.
If you see these files popping up in your directories, shut down your computer immediatly (pull the plug) and recover the unencrypted files by connecting your hard disk to another computer or using a bootdisk.