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If you're running CentOS or any other Red Hat-derived distribution, be sure that SELinux is turned off. SELinux prevents Apache from running the audit_subnet.sh script which uses nmap as root. Disabling SELinux is the quickest and simplest way to address this.
Nmap
NOTE - Version 5 or above of Nmap is required. Nmap needs to have the below command run upon it to allow its execution by users with non-root privileges.
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