NSX allows for follow the VM-security as King calls it, which sets firewall rules specific to not just networks, but virtual machines on those networks. Virtual firewalls are still used as a perimeter defense for so-called north-south traffic; that is data coming into and going out of an environment. Exostar is a Virginia-based mid-sized provider of secure hosting environments for the life sciences and aerospace industries that is excited about the potential for virtual firewall.”]
Source: https://www.csoonline.com/article/2607283/how-network-virtualization-is-used-as-a-security-tool.html