If you look at most cutting-edge network information security guidance, job #1 can be paraphrased as “Know Thy Network.” It is firmly recommended (and in much regulatory guidance demanded) that organizations keep up-to-date inventories of hardware and software assets present on their computer networks. In fact, the most current recommendation is that organizations utilize software suites that not only keep track of inventories, but monitor all critical network entities with the aim of detecting any hardware or software applications that should not be there.
Another part of network knowledge is mapping data flows and trust relationships on networks, and mapping which business entities use which IT resources and information. For this knowledge, I like to go to my favorite risk management tool: the Business Impact Analysis (BIA). In this process, input comes from personnel across the enterprise detailing what they do, how they do it, what resources they need, what input they need, what output they produce and more (see MSI blog archives for more information about BIA and what it can do for your information security program).
About now, you are probably asking what all this has to do with network segmentation. The answer is that you simply must know where all your network assets are, who needs access to them and how they move before you can segment the network intelligently and effectively. It can all be summed up with one phrase: Need to Know. Need to know is the very basis of access control, and access control is what network segmentation is all about. You do not want anyone on your network to “see” information assets that they do not need to see in order to properly perform their business functions. And by the same token, you do not want network personnel to be cut off from information assets that they do need to perform their jobs. These are the reasons network knowledge and network segmentation go hand-in-hand.
Proper network knowledge becomes even more important when you take the next step in network segmentation: enclaving. I will discuss segmentation versus enclaving in my next blog later this month.