Active Directory Flexible Authentication Secure Tunneling (FAST)

Let’s discuss Flexible Authentication Secure Tunneling (FAST).

This new feature implemented in the Windows Server 2012 KDC, provides protection against password-based dictionary attacks. FAST is an extra level of security above password lockout policies and works at the Kerberos authentication level.

What is FAST and Kerberos Armoring?

Sometimes referred to as one in the same, FAST provides offline dictionary attack prevention, that work around Kerberos errors being spoofed. If the Kerberos authentication sequence fails, authentication falls back to NTLM authentication, a less secure method.

FAST is defined by RFC 6113 and RFC 4851, to prevent spoofing Kerberos errors. FAST is also referred to as Kerberos Armoring. FAST provides a secured and protected channel to provide a protected channel between a domain-joined client and DC and involves the LSA (Local Security Authority), the Netlogon Service, and the KDC. FAST protects Kerberos pre-authentication data for the “AS_REQ” by using the LSK (randomly generated logon session key) from the TGT (Ticket Granting Ticket during the Kerberos authentication sequence) as a shared secret to fully encrypt Kerberos messages and sign all possible Kerberos errors. The shared secret provides an additional “salt” in the Kerberos authentication process. This results in increased processing time, but it does not change the Kerberos service ticket size. The shared secret provides DCs the ability to return Kerberos authentication errors, which in turn, protects against spoofing, man-in-the middle, and other attacks.

FAST and Windows Server 2008

Although Windows Server 2012 and newer domain controllers are required to support this feature, there are no requirements for the domain or forest functional levels to be at Windows Server 2012. Therefore, you can have Windows Server 2008 and Windows Server 2008 R2 domain controllers, with forest functional level on Windows Server 2008.

The only exception is if you are implementing claims across a forest trust.

FAST requirements

  • Functional levels must be at least Windows Server 2008.
  • For full support, Domain and Forest Functional Levels must be at Windows Server 2012, which means that all domain controllers must be at least Windows Server 2012.
  • The Active Directory Domain must support Claims Based Access Control (CBAC) and Kerberos Armoring policy for all Windows Server 2012 domain controllers.
  • CBAC is an authorization method granting or denying access based on an arbitrary authorization decision algorithm using data in claims.

Additional Reading on CBAC:
Authorization in Claims-Aware Web Applications and Services

The domain can be configured either to require Kerberos armoring, or use it upon request. This allows backward support for legacy clients.This can be enabled by using two Group Policy settings:

  • “Support CBAC and Kerberos armoring”
  • “All DCs can support CBAC and Require Kerberos Armoring”

Additional Reading

What’s New in Kerberos Authentication?

The Flexible Authentication via Secure Tunneling Extensible Authentication Protocol Method (EAP-FAST)

A Generalized Framework for Kerberos Pre-Authentication



Stay tuned. This is part of a release of previously unreleased documentation.

Ace Fekay
MVP, MCT, MCSE 2012, MCITP EA & MCTS Windows 2008/R2, Exchange 2013, 2010 EA & 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP – Directory Services

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Complete List of Technical Blogs:

This posting is provided AS-IS with no warranties or guarantees and confers no rights.

What is SaaS, PaaS, and IaaS?


Ace here again. With Azure gaining traction, and the whole “Cloud”computing buzzwords becoming a staple to every day life, I thought to bring some sunlight through and explain some of the offerings.

SaaS: Software as a Service

Software as a Service (SaaS) delivers business processes and applications, such as Sharepoint, CRM, collaboration, and e-mail, as standardized capabilities for a usage-based cost at an agreed, business-relevant SLA (service level agreement).

SaaS provides significant efficiencies in cost and delivery with minimal customization that represents a shift of operational risks from the consumer to the hosting provider. All infrastructure and IT operational functions are abstracted away from the consumer reducing consumer resource overhead.

The end user is the consumer, and benefits the most with SaaS with increased application uptime and performance.

PaaS: Platform as a Service

The most complex of the three, cloud platform services or “Platform as a Service,” (PaaS) delivers computational resources with an efficient and agile approach to operate scale-out applications in a predictable and cost-effective manner, through a platform, such as Windows Server 2012.

With PaaS, the application owner is the consumer. PaaS delivers application execution services, such as application runtime, storage, and integration, for applications written for a pre-specified development framework the consumer can build upon to develop, customize, and test applications. Deployment of applications is quick, simple, and cost-effective, eliminating the need to purchase underlying layers of hardware and operating systems.

PaaS is highly scalable. Consumers need not worry about platform upgrades or downtime due to maintenance.

Service levels and operational risks are shared because the consumer (customer) takes responsibility for the stability, architectural compliance, and overall operations of the application while the provider delivers the platform capability (including the network infrastructure and operational functions) at a predictable service level and cost.

One comparison between SaaS vs. PaaS is with PaaS, vendors still manage runtime, middleware, O/S, virtualization, hardware (servers & storage), and networking, but users manage applications and data. With SaaS, the users only control the software, not the platform the software is running on.

IaaS: Infrastructure as a Service

Cloud infrastructure services, known as “Infrastructure as a Service,” (IaaS), deliver computer infrastructure (such as a platform virtualization environment), storage, and networking.

IaaS abstracts hardware (server, storage, and network infrastructure) into a pool of computing, storage, and connectivity capabilities that are delivered as services for a usage-based (metered) cost. Its goal is to provide a flexible, standard, and virtualized operating environment that can become a foundation for PaaS and SaaS.

IaaS is usually seen to provide virtual server standardization by the hosting provider. The hosting provider manages virtualization and provides service level agreements (SLA) that cover the performance and availability of the virtualized infrastructure.

The consumer takes responsibility for configuration, operations, maintenance, updates, upgrades and support of the guest Operating System (OS), software, and Database (DB). Compute capabilities (such as performance, bandwidth, and storage access) are also standardized.

IaaS is an advanced state of IT maturity that has a high degree of automation, integrated-service management, and efficient use of resources.

The consumer can be the application owner and/or the IT department, and also provide middleware, application and operating system updates, upgrades and support. The benefit to the consumer is they can install any required platforms.


Click here for additional information

What does Windows 2012 R2 and Cloud OS Mean to Organizations?

It means organization can shift to efficiently manage datacenter resources as a whole, including networking, storage and computing. Organizations will be able to deliver and manage powerful apps that boost employee productivity providing faster access across private, hybrid (mixture of private & public clouds) and public clouds.

With Windows Server 2012 and System Center, an organization owns its own private cloud, and they can provide users a self-service portal to request their own multitier applications including web servers, database servers, and storage components.

Windows Server 2012 and the components of the System Center 2012 suite can be configured so service requests can be processed automatically, without requiring manual deployment of virtual machines and database server software.

Microsoft Private Cloud Fast Track

Microsoft Private Cloud Fast Track is a joint effort between Microsoft and its hardware partners to deliver pre-configured solutions that reduce the complexity and risk of implementing a private cloud, and provides and delivers flexibility and choice across a range of hardware vendor options technologies in pre-configured solutions.

For more information on Microsoft Private Cloud Fast Track, and the implementation deployment guide:

Microsoft Private Cloud Fast Track Information New and Improved, by Thomas W Shinder, MSFT, 7/27/2012

For a complete list of Reference Architecture for Private Cloud Documents:

Reference Architecture for Private Cloud



Published 10/15/2016

Ace Fekay
MVP, MCT, MCSE 2012, MCITP EA & MCTS Windows 2008/R2, Exchange 2013, 2010 EA & 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP – Directory Services

clip_image0023[2] clip_image0043[2] clip_image0063[2] clip_image0083[2] clip_image0103[2] clip_image0123[2] clip_image0143[2] clip_image0163[2]

Complete List of Technical Blogs:

This posting is provided AS-IS with no warranties or guarantees and confers no rights.