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Zero Trust Capabilities

Chapter Description

In this sample chapter from Zero Trust Architecture, uncover the foundations of Zero Trust strategy with insights into its five pillars: policy overlay, identity-centric approach, vulnerability management, access control, and visibility. Learn to identify critical capabilities, establish a solid foundation, and define risk tolerance. The authors offer a comprehensive guide for implementing Zero Trust in your organization.

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Identity Pillar

Identity is a concept to represent entities that exist on a network and is analogous to what an entity has or is. Sometimes, entities may offer a configured or known credential, while other times they do not. Identity alone is not enough to gain access to data. Determining identity is a fundamental process of authentication. Organizations using an identity alone as a basis to grant access to an object from a central authority are not aligning to a full Zero Trust strategy, because full context of the identity has not been established. As an example, possessing a driver’s license as identification does not allow anyone on an airplane. Someone or something must verify the identification matches the entity attempting to use the license against valid confirmation information.

Authentication, Authorization, and Accounting (AAA)

What is meant by the phrase “Triple A”? In simple terms, authentication is a validation of the “who” or “what” of an entity, authorization is the set of resources or data to which the authenticated entity can access, and accounting is the record of interactions that occur throughout the operation.

The first step for any entity accessing the network is to authenticate. This step requires that the entity requesting authentication—be it a person, computer, or any number of other networked devices—must provide details about itself in at least one form. These details may be provided directly by the entity, for example, using a username and password, a certificate, or a MAC address provided by the entity.

Authentication can be accomplished using multiple criteria, which is referred to as multifactor authentication. The process of authenticating does not imply the permissions to which the entity may interact. Take, for example, an ATM: anyone can walk up to one with a valid debit card and insert it into the machine. With the proper PIN code, the user will authenticate, but the possession of the card and PIN code does not explicitly provide details to which accounts that person should have access, which leads to the second “A,” authorization.

Authorization involves taking the identity of the authenticated entity and, in combination with other conditions, determining through a defined policy what level of resource or data access should be provided. Depending on the policy engine in use, these conditions can become quite granular. Some examples of additional conditions for authorizing network access might include device health or posture, a directory service group membership, time and day variables, device identity, or device ownership. Going back to the ATM example, after authentication, the customer is provided access to their accounts after a policy engine makes the necessary determinations, such as permission to view and interactions allowed with each account.

Finally, accounting is a way to record the actions an entity on the network takes for audit purposes. This includes documenting when the entity attempts to authenticate, the result of that authentication, and what interactions are made with the authorized resources and ends after the entity disconnects or logs off from the network. This accounting data is crucial for both troubleshooting and forensic purposes. In troubleshooting, it provides valuable data to help identify where in the process of AAA the entity is encountering a problem, such as why they are not getting authorized to expected data or resources. For forensic purposes, it provides the ability to understand when an entity accessed the network, what actions were taken, and when it disconnected or if it is still connected to the network.

AAA Special Conditions

It is also important to mention the challenges for AAA brought about by the rapid increase in Internet of Things (IoT) devices. In most cases, these devices operate in a more rudimentary fashion when it comes to network connectivity and may not be capable of providing a username and password for authentication, much less a certificate. In some cases, while these capabilities may be available from the device, a lack of suitable management may make use of these features not technically feasible. In either case, it is important to ensure that alternatives are available to authenticate and authorize these devices effectively and safely. Commonly, this will mean using the MAC address to authenticate the device against a database, and authorization will follow a similar set of conditions as for other entities. There are numerous efforts underway to improve the interaction of IoT devices, especially regarding enterprise networks, such as the Machine Usage Description (MUD) attribute, which provides the purpose of the device to the policy engine. Ultimately, though, these devices can be more easily spoofed when authenticated through MUD or MAC address-based paths, so caution must be taken. This lower level of confidence in positive identification and authenticating the entity in detail means special thought and care must be taken when assigning authorization to resources or data.

Certificate Authority

An alternative but slightly higher overhead for identifying devices uniquely within a network is the ability to present a certificate. A certificate, simply put, is a unique identity issued to a user or endpoint, which relies on a chain of trust. This chain of trust consists of a centralized authority being the root of the trust, and branches in a tree-like structure providing for distributed trust the world over. Issuance of a certificate to endpoints or to users provides for an “I trust this authority, and therefore I trust this entity” ability.

Certificates are typically considered a stronger method of authentication because of the ability to both prevent exportation of the identity and providing for the ability to validate the identity presented within the certificate against a centralized identity store—for example, Active Directory, which is the Microsoft Directory Store; Lightweight Directory Access Protocol (LDAP), which is an Open-Source Directory Store; or Azure Active Directory Domain Services (Azure AD DS), which is cloud-based.

By blocking the private aspects of the certificate from being exported, the certificate cannot be shared with another user or even another device, making it a secure identification mechanism. In addition, like directory service attributes, alternative names and attributes can be added into a certificate that can be used to uniquely identify an endpoint and what access the device should be provided on the network.

Certificates are typically exchanged with the policy engine via Extensible Authentication Protocol–Transport Layer Security (EAP-TLS). These certificates can be assigned to either the endpoint or the user itself. The combination of user and machine certificates creates a unique contextual identity. This contextual identity provides differentiated access based on the attributes associated to the type of identity, whether that be user, application, or machine.

Network Access Control (NAC)

A network access control system provides a mechanism to control access to the network. There are many solutions available to provide this Zero Trust Capability to maintain control of who or what accesses the network for any organization. The NAC system needs to have the ability to integrate with the other Zero Trust Capabilities, described within this chapter. The NAC system will directly participate in the Policy & Governance, Identity, Vulnerability Management, Enforcement, and Analytics pillars. Policy & Governance must influence the configuration of the NAC system.

After a device is purchased, onboarded, and identified, there needs to exist a database and policy engine to validate the identity using AAA (see the previous section). This policy engine should contain

  • Integrated authentication into a directory service

  • Endpoint posture for vulnerabilities

  • Ability to control endpoint access via policy

For example, with identity, there is a reliance upon Directory Services, or a certificate authority, which requires that the NAC system integrate with the identity store to determine and enforce AAA. NAC should utilize this identity to link vulnerability into the contextual identity, then apply and enforce controls, and then log these actions locally or to an integrated system, such as a Security Information and Event Management (SIEM) system. Logging events being generated in the NAC system requires collection of what was done and why to be able to better analyze devices on the network and their potential security implications to the network.


Provisioning is a process to acquire, deploy, and configure new or existing infrastructure throughout an organization based on Policy & Governance. Provisioning heavily impacts the decision-making process when implementing a Zero Trust strategy. Provisioning happens in multiple phases across multiple groups in the environment. All stakeholders must understand the importance of a unified policy and process.

Organizations define their own needs to meet specific requirements. A comprehensive Zero Trust strategy requires a wholistic approach that addresses the flexibility needed in the process and while maintaining tight controls that enforce the policies of the organization and regulating bodies. Proper provisioning practices dictate that a common form of tracking and visibility of access needs should be documented during all stages of the infrastructure life cycle. The following sections detail some Provisioning policy enforcement categories to consider.


Some common device types range from printers, computers, IoT, OT, specialty equipment, and managed, and not managed. Groups responsible for creating, maintaining, and executing these functions exist in almost every facet of an organization. Devices need to respect the presence of Zero Trust controls in any physical, logical, or network environment.


Users can exist in many parts of the organization but, unlike devices, should all be controlled within a defined role within the organization. User identities created for third parties must map to a role with the organization. Access for devices, people, and processes relies on these role-based user accounts. These accounts may represent multiple roles for differing functions. Zero Trust relies upon user identity, which is an important attribute in aligning policy to an action. “User” is a component of the Zero Trust Identity Capability for user attribution, assignment, and provisioning and builds a foundation for establishing trust.


A Zero Trust strategy should inform and guide all onboarding and offboarding processes within an organization of each entity. People have the potential of becoming soft targets and therefore vulnerabilities to the organization. Security threat awareness, training, and testing help build resilience within the people who work for the organization. The scope of provisioning as it relates to people applies not only to those with access to systems. Provisioning of users, devices, access, services, assets, and many other important aspects of provisioning are affected through these processes. Zero Trust controls attempt to apply attribution to any interaction with people throughout the organization, third parties, or partners. These concepts can branch out to encompass interactions with any asset by a person to any connection.


The Identity of infrastructure objects defines what an object is, what an object needs to function, and relates the object to what are valid activities of the object to support the organization.

Infrastructure provisioning processes create the pathways through which access to objects occurs. Administrators need to define what protections are needed to enable the use of the infrastructure to support the user community and the functions of their role. Administrators tasked with supporting the infrastructure mediate how and when provisioning steps interact with services and flows.


Services enable an application or a suite of applications to support and allow users to fulfill their defined user role within the organization. Without services, there is no point in giving a user access to an application. The services attribute for Identity capabilities is used to define access attributes for users to be able to execute critical functions assigned to their roles.

Service Identity provisioning processes interrelate devices, users, people, and infrastructure to further build contextual identity capabilities. Documenting the access requirements and restrictions associated to devices, users, people, and infrastructure creates policy that can be directly enforced by Zero Trust. Services rely on consistent and accurate identity information derived from provisioning to define these policies in an effective manner. Access denial and access acceptance are attained through the documentation of these identifiers and classifying what is allowed to utilize the service and under what conditions the service is being requested.

Privileged Access

Privileged access is elevated user access required to perform functions to support and manage systems. Privileged Access can be found within any portion of the infrastructure, including network appliances, databases, applications, operating systems, cloud provider platforms, communications connectivity systems, and software development. Privileged access should follow the concept of “least privileged access” and should be limited to a very small population of users. Types of users leveraging privileged access include but are not limited to database administrators, backup administrators, third-party application administrators, treasury administrators, service accounts, and systems administrators, along with network and security teams.

Privileged access introduces higher risk to data, availability, or controls. Privileged access may be leveraged by attackers to cause the most damage to an environment, ecosystem, or proprietary information, making this type of Identity what an organization should highly guard, monitor, and control.

To monitor and control privileged access, solutions are available to control this higher level of access, with timers to allow access, and stronger controls, including the logging of changes made while leveraging privileged access levels of Identity. It is recommended that organizations audit the use of privileged access on a routine basis with management oversight and signoff. Many regulations and laws require privileged access controls be put in place within an organization, with demonstrable compliance to external auditors on a routine basis. Teams should review the requirements for their organization based on regulations and legal team guidance.

Multifactor Authentication (MFA)

Multifactor authentication is the practice of leveraging factors of what a user knows (i.e., password), what a user has (i.e., managed device or device certificate), who a user is (i.e., biometrics), and what a user can solve (i.e., Captcha with problems); it is a foundational principle of Zero Trust. These aspects allow for many interpretations, and therefore, the Policy & Governance pillar needs to address the requirements of MFA within a given organization that are pushed out to all users of the environment.

Classical usernames are identifiable through email addresses, and passwords may not be well configured by users or are reused on many systems, making them easily vulnerable to brute-force attacks. By leveraging additional factors of MFA, organizations increase their resistance to attack; however, strong onboarding/offboarding of employees, interns, and contractor processes with monitoring and auditing is required to maintain control of identity stores and MFA factors and to limit unauthorized access.

In some cases, organizations may want to move to a true “passwordless” access control methodology using only device certificates to increase convenience to the user population. It is recommended that organizations review this method with legal teams and regulating bodies prior to moving to a true “passwordless” approach. For example, for most operating systems, after the user logs in to the machine, a supplicant is presented a certificate as an authentication mechanism to a policy engine. Are a user login and a device certificate enough for the organization and the regulations with which they are required to comply? These challenges to defining MFA may occur, so organizations should be specific on whether MFA is two or more of the same factors or a unique combination of factors. These details need to be specified by the organization via Policy & Governance.

Asset Identity

Asset identity is a method, process, application, or service that enables an organization to identify physical devices that interact with the organization with certainty of the actual real device type, location, and key attributes.

Organizations need to be able to identify all unique assets operating within their ecosystems. Based on the identity of the asset, the metadata adds context that will drive Policy & Governance requirements for the asset type involved or the specific asset that is necessary for a Zero Trust strategy implementation. Examples of assets that are critical for identification are not limited to servers, workstations, network gear, telephony devices, printers, security devices, and low-powered devices.

More difficult to identify are assets that include devices that do not respond to requests for unique identity like low-powered devices. These devices may not have a supplicant, or even conform with standardized RFCs dictating the format, frequency, and protocol for responses. In these cases, unique asset attributes need to be used to identify the endpoint. Passive abilities are available to identify an endpoint and have been built into standards used to manufacture devices. The unique MAC address embedded into a device’s network interface card (NIC), for example, has the first 24 of 48 bits reserved to uniquely identify the manufacturer of that endpoint against a known database of registered and reserved organizationally unique identifiers (OUI). The MAC address is a data element in standard configuration management databases.

Configuration Management Database (CMDB)

A configuration management database is an important repository of critical organization information that contains all types of devices, solutions, network equipment, data center equipment, applications, asset owners, application owners, emergency contacts, and the relationships between them all.

Whether the attribute used is the MAC address of an endpoint, a serial number unique to an aspect of the endpoint, or a unique attribute assigned to the endpoint or combination of its properties, a CMDB or an asset management database (AMDB) should exist to ensure that devices, services, applications, and data are tracked and provide critical information to respond to important events or incidents.

The information contained within the CMDB ensures that solutions may reference the data in the CMDB to control access to only authorized objects. Discreet onboarding processes are required to support a Zero Trust strategy. A description of exactly what needs to be known when an endpoint is put onto a network, with roles, responsibilities, and with updating requirements, is part of a mature organization’s Zero Trust profile.

The use of a consistent onboarding process will ensure an optimized and efficient onboarding process can be practiced. This consistent onboarding process ensures that similar provisioning practices are followed across unique vendors, and configurations are applied in a consistent way to identify entities within the network. While variations may occur in devices, even from the same vendor, consistency in identifying the device in alignment with an onboarding process will lead to a notable change in security posture. Critical elements to review when differentiating devices or device types include

  • Firmware versions

  • Base software versions

  • Individual hardware component revisions

  • Organizational unique identifier (OUI) variation for NICs

Internet Protocol (IP) Schemas

The Internet Protocol schema provides identification of services or objects via unique IP addresses. Necessary to any Zero Trust Segmentation program is having an IP address schema or plan to enable communications from workload to workload, within and outside of an ecosystem. Organizations should not focus specifically on the IP address to create a Zero Trust Segmentation strategy, but rather use an IP schema as another tool in an administrator’s toolbox to assist in identification of workloads and/or objects.

Another consideration is whether an organization should use provider-independent (PI) or provider-aggregated (PA) IP space to improve the security profile, while potentially adding an additional benefit of the organization easily moving from one provider to another.

Most organizations prefer to go with a provider-independent IP space. As stated in the technical paper “Stream: Internet Engineering Task Force (IETF)”:

a common question is whether companies should use Provider-Independent (PI) or Provider-Aggregated (PA) space [RFC7381], but, from a security perspective, there is minor difference. However, one aspect to keep in mind is who has administrative ownership of the address space and who is technically responsible if/when there is a need to enforce restrictions on routability of the space. This typically comes in the form of a need based on malicious criminal activity originating from it. Relying on PA address space may also increase the perceived need for address translation techniques, such as NPTv6; thereby, the complexity of the operations, including the security operations, is augmented.

Best practices to create a stable IP space environment include implementing an addressing plan and an IP address management (IPAM) solution. The following sections detail the three standards of IP addressing spaces that can be used to create or combine to create an IP Schema.


Internet Protocol version 4 addresses, better known as IPv4 addresses, enable workloads to communicate over public mediums utilizing a standardized 256-bit addressing standard. It is well known that the world is running out of IPv4 addresses, and this has become a driver for organizations to move to IPv6.


IPv6, with its standardized 128-bit address, is expected to be almost inexhaustive with the ability to assign an address to every square inch of the earth’s surface. This direction to implement IPv6 is difficult and should not be entered into without a well-vetted plan. This is further complicated by a need to map out significantly more address space within IPV6, typically a 56- or 64-bit allocation to a given organization, and the flows between endpoints within the address space.

To begin, a directional plan to move to IPv6 has become a legal matter and requirement for some organizations in recent years. Workload communication over IPv6 is becoming necessary, especially when working with public sector agencies. Working on a Zero Trust migration and an IPv6 migration in the same program is a daunting task. A recommendation would be to develop a roadmap to making incremental improvements over time. As part of these incremental improvements, and especially as organizations start to roll out IPv6 greenfield, a mapping of communication for how endpoints interact with each other across their respective communication domains is highly recommended. While most engineers and administrators inherited the design or design standards for IPv4 networks, organizations have a unique opportunity related to IPv6 and its ability to be part of a security strategy.

Each workload that gets an IPv6 address and can communicate over IPv6 also has a unique identity that can be associated back to IPv6. With such as a massive address space available within IPv6, identity can be tied back to the addressing, or at least associated as another tool in the network engineering toolbox.

Dual Stack

In many cases organizations need to use IPv6 address space in a “dual stack” implemen­tation that includes IPv4 addresses, as well as IPv6 addresses to enable a transition. In the case that a transition must be managed as a dual stack, this process requires double the work for administration teams. Implementing dual stack requires that each workload gets an IPv4 and an IPv6 address and can communicate over IPv4 or IPv6. This dual stack process can create a high degree of administrative overhead, including mapping out addresses, designing recognizable subnets or network architectures, and managing network devices by applying the same identity and policies to two separate addresses. Being in this dual phase of implementation tends to go on for several years or is a permanent method to manage the organization’s IP address issues.

5. Vulnerability Management Pillar | Next Section Previous Section

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