The Role of IP Addresses in Security Processes

Reflecting on IP addresses, and about factors contributing to having a proper inventory of active ones, recently led me to putting up a Twitter poll. Here are the results:

Looking at these numbers it seems that quite a few organizations struggle with maintaining a more or less accurate inventory of active addresses in their networks. At this point infosec purists may stress the importance of a thing called asset management (I mean there’s a reason why it’s the 1st function in the 1st category of the NIST Cybersecurity Framework, right? ;-), but I for one just felt I should reflect a bit more on the role of IP addresses for certain processes within an organization. Not least as related aspects and questions may become even more important once a whole new class of addresses enters the corporate infosec ring: enter IPv6.
Let’s hence imagine there’s a certain number of systems in your organization’s network, and some of those systems are now getting IPv6. Which security processes could potentially be affected (read, in a sufficiently large organization: which teams should know about the ongoing IPv6 effort? ;-).

From a simplified perspective security processes can be grouped into the following categories (those interested in other categories find some here):

  • preventative ones (‘avoid that a threat can materialize against an asset’). For our purpose here let’s take filtering of network traffic and patch management as examples.
  • detective ones: these can include the detection of deviations of a desired security state like the detection of vulnerabilities (=> vulnerability management) or the detection of security violations (e.g. by system-local mechanisms like log files or agents, or by means of network [security] telemetry).
  • reactive security processes, e.g. incident response.

Traffic filtering is usually mainly done in one of these two flavors:

  • gateway-based filtering (firewalls or router ACLs). Once this is used it may be of (security) interest if there’s at least one active IP/system of a specific address family (here: IPv6) in use within a given subnet.
  • local packet filtering. Once the respective rules are centrally managed those in charge better know about active IP speakers, I’d say. Once those are not centrally managed (which is the case in many environments), first+foremost one might ask: who manages them at all? 🤔😂
    Kidding aside, evidently for those entities responsible for the configuration of local packet filters knowledge of active addresses of all address families is probably valuable.

To properly perform patch management one usually has to know: which systems are out there? And how does one identify those systems? For example, in environments using MS Active Directory probably all domain members can be identified by some AD-inherent logic, and other systems might be identifiable by means of their FQDNs. Still it’s a safe assumption that at least some fraction of to-be-patched systems are identified by their IP address(es), so having a proper inventory can be of help here, too.
Evidently in the course of patch management one might not only be interested in actively running systems, but also & namely in their OS + software components and their respective versions. Coming up with that type of information commonly falls into the realm of vulnerability management. The vast majority of vulnerability management tools & frameworks I’m aware of primarily use addresses as identifiers of systems. From that angle an accurate inventory of addresses certainly helps. The advent of IPv6 might bring some extra challenges here, as simply scanning IP subnets for active systems (in order to subsequently subject those to vuln scanning) doesn’t work any longer with IPv6, so the need of a proper source of truth becomes more crucial (I already discussed this in the IPv6 Security Best Practices post).

Finally in the context of incident response generally situational awareness (what’s happening, which assets are affected, what’s the source of certain things going on etc.) is needed. I could imagine that the ability to map IP addresses to systems can be helpful here (for identification, evaluation, follow-up), so a proper IP address inventory might be of value, so to say.

tl:dr: having a understanding of active IP addresses within an organization affects (at least) the following security controls/processes:

  • (potentially) traffic filtering
  • (potentially) patch management
  • (definitely) vulnerability management
  • (definitely) detection of security violations
  • (definitely) incident response

So when deploying IPv6 in an environment, talking to the owners of these processes is needed, in order to make sure that IPv6 does not lead to an increased risk exposure.

Published by Enno

Old-school networking guy with a certain focus on network security. This blog is a private blog and it contains private musings, even though I have a day job around the Internet Protocol. I leave it to the valued reader to guess which version of it ;-). Some tweets on related topics at

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