I have several machines on a domain all running a 'powershell.exe' process as system and its smashing the pants off the servers. They're all 100% CPU and, naturally, ground to a halt.
This is Windows server 2012 R2 on HyperV virtual machines.
Killing the process fixes the issue for a while, but then later the CPU smashes the ceiling again and everything just grinds to a halt.
This powershell process was also running on the underlying hypervisor, causing further issues.