What is a Next-Gen Host-Based Firewall and why would anybody care?

Host-Based Firewalls are a simple technology that is generally used to prevent unwanted inbound traffic by port number. They don’t play a significant role in most enterprise security programs because its too much work to manage policies for each individual host. Instead, organizations prefer to enforce policies with network firewall devices that can protect large numbers of hosts from a single location.

New technologies have recently started to change this by providing a way to manage large numbers of individual endpoint firewall policies from a central system. We call these solutions Next-Generation Host-Based Firewalls, although the term Micro-Segmentation is also sometimes applied to this space. There are two primary trends that are driving this change:

Cloud Adoption: Workload mobility combined with the absence of traditional network architecture in cloud environments has meant that in some cases, firewall policies have to be managed on an individual endpoint basis, and there need to be tools that facilitate this.

Sophisticated Targeted Attacks: These days the initial point of infection for an attacker within a network is just a foothold that is used to spread internally in search of vital information to steal or encrypt with ransomware. This fact has driven organizations to pursue a Zero Trust approach to network security, where hosts inside the perimeter are not considered inherently more trustworthy than hosts outside the perimeter. The ultimate Zero Trust model means that every host is capable of defending itself, and tools are needed to orchestrate that defense.

As various Next-Generation Host-Based Firewall solutions have come on the market, the market has begun to define itself around a few key features or characteristics that all of these products share:

Central Policy Management: Obviously a “table stakes” requirement for these solutions is the ability to create a policy for a large number of individual endpoints from a central policy management tool. These policies are managed in one place, but enforced in many places — by each individual endpoint system.

Network Visualization:Crafting a security policy for large numbers of endpoints can be challenging. Next-Generation Host-Based Firewalls typically collect logs of network traffic from each endpoint and can provide the user with the ability to see and explore their network and it’s interrelationships. This can be a powerful tool for investigating security incidents as well as building policies that can contain them.

Abstract Policy Making: Traditional Firewalls enforce policy based on IPs, ports, and protocols. This can be inadequate for dealing with the complex set of interactions that occur on an internal network where workloads and workstations can move around. Typically, Next-Generation Host-Based Firewalls allow policies to be defined based on the identity of a user or of a workload or application, regardless of what system, IP or port is involved. This makes policy definition much simpler by allowing the user to express rules in human terms.

In our view there are three main architectural approaches to building Next-Generation Host-Based Firewalls. In describing these architectures, we use the words “active” and “passive” to refer to the role that the central policy management system takes in making case-by-case enforcement decisions.

Passive: A Passive Next-Generation Host-Based Firewall system is capable of pushing traditional, static firewall policies out to endpoints, but the central policy management system takes no direct role in policy enforcement. When new connections are made or received by each endpoint, the endpoint evaluates them against the policy it has been given and chooses whether to allow or block them.

This architecture has the advantage of imposing minimal latency at connection establishment and being resilient against temporary loss of connectivity between endpoints and the central policy manager.

Active: Instead of pushing static policies out to endpoints, an Active Next-Generation Host-Based Firewall makes enforcement decisions at a central controller. When each new connection is made or received by each endpoint, the endpoint contacts the controller and the controller decides whether or not the endpoint should allow or block, on a case-by-case basis. In this sense the controller is playing an active role in making enforcement decisions.

This architecture has the advantage of being able to adapt policy enforcement decisions immediately to changing circumstances on the network, such as when a host moves to a different network segment, or when a decision has been made to quarantine a compromised host. This adaptability is necessary to enable micro-segmentation in traditional office environments where rapid changes are commonplace. While there is some cost associated with this architecture, the latency and availability impacts are comparable to those imposed by the use of DNS servers.

Hybrid: A hybrid solution combines the best of both architectural approaches, allowing for dynamic policies to be enforced in real time by a central controller, with static backups in place that can make rapid decisions when the controller cannot be reached.

The OPAQ Cloud delivers Active & Hybrid Next-Generation Host-Based Firewalls. We believe that these technologies play a key role in securing the hybrid networks of today, especially as workloads move to the cloud and networks de-perimeterize. They enable enterprises to pursue a true Zero Trust approach to network security — where hosts on the internal network are not inherently trusted. The Zero Trust model is a prerequisite for defense against sophisticated threat actors, and a step toward totally new kinds of enterprise network architectures where perimeter defenses are no longer required.