Monday, November 14, 2016

Rethinking Micro-segmentation

Traditional Security Architectures

Traditional security architectures enforce security policy at rigidly defined trust boundaries. At the most basic level, this is the perimeter of the network. A firewall sits between the untrusted public Internet and the trusted private network. If inbound access from the Internet is required, a DMZ is often created to segment Internet exposed resources from the trusted internal network. A network can be further segmented using additional zones on the perimeter firewall, access-lists on distribution switches, and additional layers of security at various points in the network.

In this traditional model, as security increases, so does configuration complexity, management overhead, and margin for human error. In addition, implicit trust between devices on a network segment is inherent to traditional security architectures. If one device is breached, an attacker can use the compromised device to launch an attack against other devices on the same network segment. Therefore, traditional security architectures are often ill equipped to secure east-west traffic in a modern data center.

What is micro-segmentation?

In two words: Trust nothing. The goal is to eliminate implicit trust and apply security policy between all devices within the purview of the micro-segmentation solution. By using this zero-trust model, micro-segmentation solutions aim to prevent attackers from moving laterally through a network after breaching an initial target.

There are a few fundamentally different approaches to micro-segmentation in the data center. Several current micro-segmentation solutions are built into larger data center orchestration and automation platforms. I'll avoid mentioning specific products, because comparisons often end up like those of vi vs. Emacs or which is the best Linux distribution.

That said, the solutions I am most familiar with enforce security policy in one of two ways:
    • Enforce policy in the network device and/or vSwitch
    • Enforce policy in the hypervisor kernel

Despite where the actual enforcement occurs, at a high level the micro-segmentation functionality itself is comparable. An engineer logs into a controller, defines a security policy, and centrally pushes this security policy to a number of devices in order to restrict traffic between endpoints. These endpoints can be baremetal servers, VMs, containers, or other resources supported by the micro-segmentation platform. The fundamental difference is the point of policy enforcement - hypervisor, vSwitch, or network device.