Nonsense. I'm doing cybersecurity analysis for a Navy program this very day. To the person that says "The attackers did use stealthy persistence techniques often called 'rootkits'" -- you know exactly nothing about what you're talking about.

A rootkit is the means to obtain "root" permissions which is an exclusive feature of UNIX/Linux operating systems. Powershell is a Windows product... these systems are Windows based. No rootkit. Period.