“Virtual Machine Forensics”

Go to the Forensic Focus website to read the article titled “Virtual Forensics: A Discussion of Virtual Machines Related to Forensics Analysis,” dated 2008, located at http://www.forensicfocus.com/downloads/virtual-machines-forensics-analysis.pdf.
Determine what you perceive to be the greatest challenge when dealing with virtual machines from a system forensics perspective. Provide a rationale for your response.
Describe how virtual machines can be used in a forensics investigation. Using the Internet, provide a link to a set of tools that is considered a forensic imager that could be launched using virtualization.