A portion of the ntop Makefile, namely the "install-data-local" target in
the root-level Makefile.am, fails to utilize the DESTDIR variable.  Thus, a
build as root will cause various ntop HTML and data files to be installed
into /usr/sbin and /usr/etc rather than in the buildroot.  Worse yet, a
build as any other user will fail.  Moreover, the resultant RPM will not
contain the /usr/sbin/ntop-cert.pem file, and indeed the RPM from
updates.redhat.com is missing that file.  There is a similar problem with
the plugins (/usr/sbin/plugin/*.so) which are also missing from your RPM.

I will attach a fixed spec file and a patch which will correct the
problems.