The story
Computer virtualization has been in use on mainframe computers since the IBM VM/370 platform released in the early 1970s. VM technology became more widely available with the release of VMware Workstation in 1999, and the VMware Server line in 2001. It was estimated that 50% of workloads would be running inside virtualized environments by 2012
Whenever virtualization technology includes a hypervisor, then a virtual network can be created within the hypervisor layer to transparently network all the virtual machines operating under a single virtualized environment. This "virtual network" provides all the benefits and administrative responsibilities of a physical network, with the addition of some new challenges. The founders of Altor Networks became aware early on that adoption of virtualization technologies in data centers had been accelerating for many years and several problems in virtual network security in particular became apparent:
The virtual environment had some unique security characteristics and needs;
Those needs were not being addressed effectively by IT security vendors; and
Traditional security technologies were ill-equipped to protect virtualized IT resources.
It was decided that the way to address these challenges was to provide a solution that operated entirely within the virtualized environment as a purpose-built appliance to provide firewalling and other security services directly inside the virtual network without recourse to external hardware firewalls or intrusion detection appliances, or any associated VLAN rerouting out of the virtual network to the physical network and back again.
From Wikipedia’s article on Altor Networks, shared under CC BY-SA 4.0.4