Segmentation: The Neglected (Yet Essential) ControlFailure to deploy measures to contain unauthorized intruders is a recipe for digital disaster.
Throughout the past decade, the information security profession has pursued an approach centered around protecting the network perimeter. While this proactive strategy has become the foundation of most enterprise programs, organizations must be equally capable of reacting to attacks by containing intruders once they have entered the network.
Although identifying and mitigating perimeter threats is essential, the fact remains that cybercriminals and nation-state actors are, with alarming frequency, defeating the most-hardened networks. Therefore, it is imperative that practitioners acknowledge this dynamic and deploy containment measures to isolate intrusions.
Network segmentation is a critical weapon in the escalating battle to protect against unauthorized access.
The vast majority of cyberattacks originate within the most vulnerable area of an organization, the user environment. Once the initial compromise occurs through the use of stolen credentials or the successful delivery of a social engineering overture, those launching the attack enjoy a foothold from which to search for critical platforms and sensitive data. By dividing a network into segments and restricting lateral access, security teams are capable of containing intruders and dramatically reducing the entity's attack surface.
When intruders enter an inadequately segmented, or "flat," network, they often enjoy unbridled movement and will eventually gain access to payment applications, sensitive databases, and critical infrastructure systems. Through segmentation, these critical technologies may be isolated and thereby protected.
Although many high-profile and destructive cyber campaigns have been attributed to poor segmentation, perhaps the most widely reported incident was the 2013 Target breach. According to multiple sources, a group based in Eastern Europe breached the retailer's perimeter by first stealing credentials from one of the company's service providers, an HVAC vendor.
Once inside the system that monitors Target's heating and air conditioning functions, the cybercriminals were able to proceed, without detection, to the point-of-sale environment. Ultimately, malware was installed on approximately 36,000 payment terminals, allowing for the hackers to steal 40 million credit and debit card numbers from unsuspecting shoppers.
This scenario is the digital equivalent of a bank robber entering the lobby of a major financial institution and proceeding, unimpeded and without being noticed, to a vault containing its customers most-valuable items.
The Path Forward
Management has long avoided the deployment of comprehensive network segmentation due to a variety resource and operability concerns. Recently, however, dramatic advances in enterprise software solutions provide practitioners with scalable, customized options to address this issue.
Prior to implementing a segmentation strategy, a clear consensus must be reached regarding an organization's sensitive data and critical platforms. Given that isolating these environments will be the ultimate goal, there can be no ambiguity on this issue. Also, it is necessary to map the existing communication paths and application dependencies within the network. Once these preliminary tasks have been completed, the following segmentation options may be considered:
Environmental: Isolates the most vulnerable environments, such as user and development, from the rest of the network and prevents intruders from breaching the low-hanging fruit and then moving laterally. This is known as the "coarsest" form of segmentation and should exist in every organization.
Application: Ensures that certain high-value applications are insulated from all others and provides an additional roadblock for attackers attempting to travel across applications.
Process: The "finest-grain" form of segmentation ensures that only active communications channels may be used and prevents any use of dormant paths.
The rapidly evolving nature of the cyber-threat landscape requires adaptive information security professionals. Although preventing intrusions is, and should remain, a primary goal, failure to deploy measures to contain unauthorized intruders is a recipe for digital disaster.
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John Moynihan, CGEIT, CRISC, is President of Minuteman Governance, a Massachusetts cybersecurity consultancy that provides services to public and private sector clients throughout the United States. Prior to founding this firm, he was CISO at the Massachusetts Department of ... View Full Bio