There is a script on each McAfee SIEM appliance designed to securely delete all data on the box. You can SSH into the appliance and type "ShredTheSystem". This will securely overwrite all data files, and wll also delete many key operating system files. IMPORTANT: this will render the box COMPLETELY UNUSEABLE until you re-image it with the proper ISO. The primary purpose of this script is to allow customers to wipe devices before returning them to McAfee for hardware issues, or at the end of an evaluation, but it can be useful for other purposes as well.
Returning a box to factory default requires the ISO image for your appliance. You can obtain the ISO image and reimage process from McAfee Support.