SymptomsParallels H-Sphere Control Panel can not pass PCI (payment card industry) scan because Linux distributives by default allow access into all ports. That may cause various vulnerabilities for services working on these ports.
Filter incoming traffic to all ports not used by Parallels H-Sphere or not used in your cluster from outside.
All ports (and services) used by Parallels H-Sphere Control Panel and theirs accessibility status from outside is described on the document
"Parallels H-Sphere Installation Guide" -> "Preparing for Parallels H-Sphere Installation" -> "Required Components and Configuration" -> "Ports"
All other ports access should be restricted strongly. Use iptables/ipchains for that.