Thank you for your fast answer!
Yes, root privileges are also required, did not have in mind (also had to work with Ubuntu in the last time where you just have to enter yout user password to get higher privileges). If an intruder has your root password or can exploit something to get these, you're toast anyway.
For example, at work we use RHEL and CentOS, with an absolutely minimalistic set of programs and tools (only the stuff we really need). Furthermore, you have to start a proxy service on another system to gain access to the internet (the systems do not have any "direct" way to the internet).
All our workstations run Fedora, also requires that proxy to gain interet access, but there I needed GCC as well as the kernel sources to compile the real-time protection of an anti-virus software.
At home, I am using e. g. VirtualBox. I used to use the version from the repos, but I had some issues back then (package disappeared after kernel update as far as I remember, but does not matter here). Due to this, I decided to use the version from the website which also requires GCC and the kernel sources.
Of course, a firewall and SELinux are installed on all the systems mentioned above, the latter should also report suspicious activity.
So, that's what I will do:
After upgrading to Fedora 26 I will use the VirtualBox version from the standard repos again and avoid GCC as good as possible or when I need it, uninstall it when done.