An Interesting take on Mapping an Attack Surface

Security often lives in one of two states. It’s either something “I” take care of, because my organization is so small there isn’t anyone else taking care of it. Or it’s something those folks sitting over there in the corner take care of because the organization is, in fact, large enough to have a separate security team. In both cases, however, security is something that is done to networks, or something thought about kind-of off on its own in relation to networks.

I’ve been trying to think of ways to challenge this way of thinking for many years—a long time ago, in a universe far away, I created and gave a presentation on network security at Cisco Live (raise your hand if you’re old enough to have seen this presentation!).

Reading through my paper pile this week, I ran into a viewpoint in the Communications of the ACM that revived my older thinking about network security and gave me a new way to think about the problem. The author’s expression of the problem of supply chain security can be used more broadly. The illustration below is replicated from the one in the original article; I will use this as a starting point.

This is a nice way to visualize your attack surface. The columns represent applications or systems and the rows represent vulnerabilities. The colors represent the risk, as explained across the bottom of the chart. One simple way to use this would be just to list all the things in the network along the top as columns, and all the things that can go wrong as rows and use it in the same way. This would just be a cut down, or more specific, version of the same concept.

Another way to use this sort of map—and this is just a nub of an idea, so you’ll need to think about how to apply it to your situation a little more deeply—is to create two groups of columns; one column for each application that relies on network services, and one for network infrastructure devices and services you rely on. Rows would be broken up into three classes, from the top to bottom—protection, services, and systems. In the protection group you would have things the network does to protect data and applications, like segmentation, preventing data exfiltration, etc. In the services group, you would mostly have various forms of denial of service and configuration. In the systems group, you would have individual hardware devices, protocols, software packages used to make the network “go,” etc. Maybe something like the illustration below.

If you place the most important applications towards the left, and the protection towards the top, the more severe vulnerabilities will be in the upper left corner of the chart, with less severe areas falling to the right and (potentially) towards the bottom. You would fill this chart out starting in the upper left, figuring out what each kind of “protection” the network as a service can offer to each application. These should, in turn, roll down to the services the network offers and their corresponding configurations. These should, in turn, roll across to the devices and software used to create these services, and then roll back down to the vulnerabilities of those services and devices. For instance, if sales management relies on application access control, and application access control relies on proper filtering, and filtering is configured on BGP and some sort of overlay virtual link to a cloud service… You start to get the idea of where different kinds of services rely on underlying capabilities, and then how those are related to suppliers, hardware, etc.

You can color the squares in different ways—the way the original article does, perhaps, or your reliance on an outside vendor to solve this problem, etc. Once the basic chart is in place you can use multiple color schemes to get different views of the attack surface by using the chart as a sort of heat map.

Again, this is something of a nub of an idea, but it is a potentially interesting way to get a single view of the entire network ecosystem from a security standpoint, know where things are weak (and hence need work), and understand where cascading failures might happen.