Experience with Center for Internet Security (CIS) benchmarks and other hardening techniques to secure virtual operating systems (Windows – Server 2016, Vista/7/8/10 and Linux – Ubuntu 14/16, Debian 8) against common vulnerabilities and exposures (CVEs) from open services. Also simulated network topologies containing nodes (routers, switches, firewalls) based on OSI model with Cisco PacketTracer/NetAcad.