AD modernization versus misconceptions, misconfigurations
When AD was first introduced more than two decades ago, the design of AD domains was heavily influenced by bandwidth limitations and replication concerns. These constraints, combined with object limits and migration challenges from legacy Windows NT 4 domains, resulted in the adoption of multiple domains within a forest design.
At the time, a common security misconception was that a domain should be the security boundary for independent units inside the organization. Earlier in my career, for example, I worked for a financial institution that adhered to these best practices and had over a dozen AD domains in its main forest.
With this misconception came a false sense of security because any compromised domain in this scenario would lead to a fully compromised environment.
Fast forward 20 years. We now know that domains are not a security boundary. In fact, multiple domains create management challenges that in turn present unnecessary security exposures.
AD modernization versus accumulated technical debt
Another major security exposure involves managing multiforest environments. Many organizations have accumulated such environments over the years, often through mergers and acquisitions.
As with many systems, accruing technical debt is common. But the sensitivity of AD makes the associated security risk much higher.
Multiforest environments create multiple management and security challenges for IT and identity management teams. For example, consider trusts that are set between various forests. If the least secure forest is breached, it can be used as a beachhead to more sensitive environments.
A more secure resolution: AD consolidation
The greatest security improvement can be achieved by collapsing as many forests as possible into a single forest. Not only does this consolidation make a positive impact on the security posture of the organization, but it also often reduces total management costs by eliminating the more complex, distributed multiforest environment.
Of course, such consolidation requires careful planning, taking into consideration the impact on applications, security principals, and the like. Organizations must also consider the sensitivity of the different environments. Best practice is to separate environments according to sensitivity level. For instance, separate your dev/test environment from production.
Modern AD forest environments should also collapse domains into organizational units (OUs) if independent management is required or into groups if there is no need for independent units. This setup enables the organization to reduce the number of domains that need to be managed.
Once the environments are consolidated, the organization can use one location to enforce its security policies via Microsoft Group Policy objects (GPOs), Intune, System Center Configuration Manager (SCCM), or other means. You can also consolidate the management of permissions and all other aspects of a properly secured identity environment.
Where to begin your secure AD migration
As you approach the critical task of AD modernization, keep security in mind. Your goal is a more secure and easier-to-manage environment. But you should also ensure that the migration process itself is secure. Migration is a sensitive time; avoiding security exposures is critical.
Start by scanning and assessing the security maturity of the environments that you plan to combine. Continue that process as part of your migration plan so that you do not introduce new security posture weaknesses as you migrate to new domains.
You can use free AD security assessment tools like Purple Knight and Forest Druid for these initial assessments. If your environment requires deeper attention, consider calling in an external cybersecurity team for assistance.
Also give critical consideration to your migration tools, especially in larger environments. Prioritize tools that are easy to use; complexity creates potential security exposures. Look for tools that prevent additional exposures within your identity systems (e.g., sensitive databases), which can be abused. A simple, secure tool like Semperis Migrator for AD meets these requirements.
Learn more about AD security and migration
You can learn more about the AD security and migration tools mentioned earlier at the following links:
