|Industry||Virtual network security|
|Headquarters||Redwood Shores, California, USA|
|Key people||Amir Ben-Efraim, CEO|
|Products||Virtual security appliance, virtual firewall|
|Net income||Not stated|
|Employees||Around 50 (2010) in two countries|
Altor Networks, Inc., a Juniper Networks Company, is a provider of security for virtual data centers and clouds. The company developed the world’s first firewall purpose-built for virtual networks, a software security "appliance" that runs in a virtualized environment and enforces security policy on a per-virtual-machine basis. Data center administrators could pinpoint a broad range of virtual network security comprises and create roles-based security policies. Security policies could be continuously enforced on individual virtual machines (VM), even as they moved throughout the virtualized data center.
Headquartered in Redwood Shores, California, USA, Altor was founded in 2007 by security and networking experts from Check Point Software, Cisco and Oracle Corporation, and has received funding from Accel Partners, DAG Ventures, Foundation capital, and Juniper Networks. On December 6, 2010 Juniper Networks announced it has acquired Altor Networks.
Computer virtualization has been in use on mainframe computers since the IBM VM/370 platform  release 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.
Altor released the Virtual Network Security Analyzer (VNSA) as a tool to monitor and analyze virtual network traffic in March 2008, followed on by the Altor VF 1.0 (which included the VNSA as a module) in October 2008. Integrated signature-based network intrusion detection was incorporated into the Altor VF 3.0 release in September 2009. The release of Altor v4.0 now leverages virtual machine introspection to bring visibility to internal virtual machine states for compliance assessment and automated security enforcement.
- Altor VNSA (Virtual Network Security Analyzer), released March 2008 (now part of Altor VF)
- Altor VF 1.0 (Altor Virtual Firewall), released October 2008
- Altor VF 2.0, released March 2009
- Altor VF 3.0, released September 2009
- Altor v4.0, released June 2010
Additional reading 
-  Juniper Networks announces acquisition of Alto Networks
-  Creasy, RJ, "The Origin of the VM/370 Time-sharing System" [PDF]
-  VMware company history
-  Perilli, Allesandro "50% of workloads will run inside virtual machines by 2012 says Gartner", Virtualization.info
- "The Low Down on Virtualization Security" Tek-Tools Software, June 2009
-  "Virtual Machine Software Market Grew 67 percent in 2005, Says IDC" CIO Weblog, October 2006