Active Directory Domain Services 2016

In this article, by Dishan Francis, the author of the book Mastering Active Directory, we will see AD DS features, privileged access management, time based group memberships. Microsoft, released Active Directory domain services 2016 at a very interesting time in technology. Today identity infrastructure requirements for enterprise are challenging, most of the companies uses cloud services for their operations (Software as a Service—SaaS) and lots moved infrastructure workloads to public clouds.

(For more resources related to this topic, see here.)

AD DS 2016 features

Active Directory domain service (AD DS) improvements are bind with its forest and domain functional levels. Upgrading operating system or adding domain controllers which runs Windows Server 2016 to existing AD infrastructure not going to upgrade forest and domain functional levels. In order to use or test these new AD DS 2016 features you need to have forest and domain function levels set to Windows Server 2016. The minimum forest and domain functional levels you can run on your identity infrastructure depend on the lowest domain controller version running.

For example, if you have Windows Server 2008 domain controller in your infrastructure, even though you add Windows Server 2016 domain controller, the domain and forest functional level need to maintain as Windows Server 2008 until last Windows Server 2008 demote from the infrastructure.

Privileged access management

Privileged access management (PAM) is one of the best topics which is discussed on presentations, tech shows, IT forums, IT groups, blogs and meetings for last few years (after 2014) around identity management. It has become a trending topic especially after the Windows Server 2016 previews released. For last year, I was travelling to countries, cities and had involved with many presentations, discussions about PAM. 

First of all, this is not a feature that you can enable with few clicks. It is a combination of many technologies and methodologies which came together and make a workflow or in other words way of living for administrators. AD DS 2016 includes features and capabilities that support PAM in infrastructure but it is not the only thing. This is one of the greatest challenge I see about this new way of thinking and new way of working. Replacing a product is easy but changing a process is more complicated and challenging.  

I started my career with one of the largest north American hosting company around 2003. I was a system administrator that time and one of my tasks was to identify hacking attempts and prevent workloads getting compromised. In order to do that I had to review lot of logs on different systems. But around that time most of the attacks from individual or groups were to put names on websites and prove that they can hack websites. Average hacking attempts per server was around 20 to 50 per day. Some collocation customers were even running their websites, workloads without any protection (even though not recommended). But as the time goes year by year number of attempts were dramatically increased and we start to talk about hundreds of thousands attempts per day. The following graph is taken from latest Symantec Internet Security Threat Report (2016) and it confirms number of web-based attacks increased by more than 117% from year 2014. 

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Web attacks blocked per month (Source - Symantec Internet Security Threat Report (2016))

It has not only changed the numbers, it also changed the purpose of attacks. As I said in earlier days it was script kiddies who were after fame. Then later as users started to use more and more online services, purpose of attacks changed to financial values. Attackers started to focus on websites which stores credit card information. For last 10 years, I had to change my credit card 4 times as my credit card information were exposed along with the websites I had used it with. These type of attacks are still happening in the industry. 

When considering the types of threats after the year 2012, most of the things changed. Instead of fame or financial, attackers started to target identities. In earlier days, the data about a person were in different formats. For example, when I used to walk into my medical center 15 years ago, before seeing the doctor, administration staff had to go and find the file containing my name. They had number of racks filled with files and papers which included patient records, treatment history, test reports, and so on. But now things have changed, when I walk in, no one in administration need to worry about the file. Doctor can see all my records from his computer screen with few clicks. So, the data is being transformed into the digital format. More and more data about people is transforming into digital formats. In that health system, I become an identity and my identity is attached to the data and also to a certain privileges. Think about your bank, online banking system. You got your own username and password to type in, when you log in to the portal. So, you have your own identity in the bank system. Once you log in, you can access all your accounts, transfer money, make payments. Bank has granted some privileges to your identity. With your privileges, you cannot look into your neighbor’s bank account. But your bank manager can view your account and your neighbor’s account too. That means the privileges attached to the bank manager’s identity is different. Amount of data which can be retrieved from systems are dependent on the identity privileges.

Not only that, some of these identities are integrated with different systems. Industries use different systems related to their operations. It can be email system, CMS or billing system. Each of these systems hold data. To make operations smooth these systems are integrated with one identity infrastructure and provides single sign-on experience instead of using different identities for each and every application. It is making identities more and more powerful within any system. For an attacker, what is more worth? To focus on one system or target on identity which is attached to data and privileges to many different systems? Which one can make more damage? If the identity which is the target, has more privileged access to the systems, its a total disaster.

Is it all about usernames, passwords or admin accounts? No it's not, identities can make more damage than that. Usernames and passwords are just making it easy. Just think about the recent world famous cyber-attacks.

Back in July 2015, a group called The Impact Team threatened to expose user account information of Ashley Madison dating site, if its parent company Avid Life Media didn't shut down the Ashley Madison and Established Men websites completely.

For example, Ashley Madison website hack, is it that the financial value made it more dangerous? It was the identities which made damages to people’s lives. It was just enough to expose the names and make someones life to be humiliated. It ruined families and children lost their parents love and care. It proves it’s not only about permissions attached to an identity, individual identities itself are more important in modern big data phenomenon.

It’s only been few months from the USA presidential election and by now we can see how much news it can make with a single tweet. It wasn’t needed to have special privileges to do a tweet, it was the identity which made that tweet important. In other hand if that twitter account got hacked and someone tweeted something fake on behalf of the actual person who owns it, what kind of damage it can make to whole world? In order to do that, does it need to hack the Jack Dorsey’s account? Value  of individual identity is more powerful than twitter CEO.

According to following latest reports, it shows that majority of information exposed by identity attacks, are people names, addresses, medical reports, and government identity numbers.

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Source - Symantec Internet Security Threat Report (2016)

The attacks targeted on identities are rising day by day. The following graph shows the number of identities been exposed, compared to the number of incidents.

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Source - Symantec Internet Security Threat Report (2016)

In December 2015, there were only 11 incidents and 195 million identities were exposed. It shows how much damage these types of attacks can make. 

Each and every time this kind of attack happens, most common answers from engineers are “Those attacks were so sophisticated”, “It was too complex to identify”, “They were so clever”, “It was zero-day attack”. Is that really true? 

Zero-days attacks are based on unknown system bugs, errors to vendors. Latest reports show the average time of explores are less than 7 days and 1 day to release to patch. Source - Symantec Internet Security Threat Report (2016)

Microsoft Security Intelligence Report Volume 21 | January through June, 2016 report contains the following figure which explains the complexity of the vulnerabilities. It clearly shows the majority of the vulnerabilities are less complex to exploit. High complexity vulnerabilities are still less than 5% from total vulnerability disclosures. It proves the attackers are still after low hanging fruits.

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Source: Microsoft Security Intelligence Report Volume 21 | January through June, 2016

Microsoft Active Directory is the leader in identity infrastructure solution provider. With all this constant news about identity breaches, Microsoft Active Directory name also appears. Then people start to question why Microsoft can’t fix it? But if you analyse these problems, it’s obvious that just providing technology rich product is not enough to solve these issues. With each and every new server operating system version, Microsoft releases new Active Directory version. Every time it contains new features to improve the identity infrastructure security. But when I go for the Active Directory released project, I see a majority of engineers not even following the security best practices defined by 10 years’ older Active Directory version.

Think about a car race, its categories are usually based on the engine power. It can be 1800cc, 2000cc or more. In the race, most of the time it's the same models and same manufactured cars. If it's same manufacture, and if it's same engine capacity how one can win and the other lose? It’s the car tuning and the driving skills which decide a winner and loser. If Active Directory domain service 2016 can fix all the identity threats that’s really good but giving a product or technology doesn’t seem to be work so far. That’s why we need to change the way we think towards identity infrastructure security. We should not forget we are fighting against human adversaries. The tactics, methods, approaches they use, are changing every day. The products we use, do not have such frequent updates but we can change their ability to execute an attack on infrastructure by understanding fundamentals and use the products, technologies, workflows to prevent it.

Before we move into identity theft prevention mechanism let’s look into typical identity infrastructure attack.

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Microsoft Tiered administration model is based on three tiers. All these identity attacks are starting with gaining some kind of access to the identity infrastructure and then move laterally until they have keys to the kingdom which is domain admin or enterprise administrator credentials. Then they have full ownership of entire identity infrastructure.

As the preceding diagram shows that the first step on identity attack, is to get some kind of access to the system. They do not target domain admin or enterprise admin account first. Getting access to a typical user account is much easier than domain admin account. All they need is some kind of beach head. For this, still the most common attack technique is to send out phishing email. It’s typical that someone will still fall for that and click on it. Now they have some sort of access to your identity infrastructure and next step is to start moving laterally to gain more privileges. How many of you completely eliminated local administrator accounts in your infrastructure? I’m sure the answer will be almost none. Sometimes, users are asked for software installations, system level modifications frequently in their systems and most of the time engineers are ending up assigning local administrator privileges. If the compromised account used to be local administrator its becomes extremely easy to move to the next level. If not, they will make systems to misbehave. Then who will come to the rescue? It's the super powered IT help-desk peoples. In lots of organizations, IT help-desk engineers are domain administrators. If not at least local administrators to the systems. So, once they receive the call about a misbehaving computer, they RDP or login locally using the privileged account. If you are using RDP, it always sends your credentials via clear text. If the attacker is running any password harvesting tool it's extremely easy to capture the credentials. You may think if account (which is compromised) is a typical user account how it can execute such programs. But Windows operating systems are not preventing users from running any application on its user context. It will not allow to change any system level settings but it will still allow to run scripts or user level executable.

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Once they gain access to some identity in organization, the next level of privileges to own will be Tier 1. This is where the application administrators, data administrators, SaaS application administrators accounts live. In today's infrastructures, we have too many administrators. Primarily we have domain admins, enterprise administrators, then we have local administrators. Different applications running on the infrastructure have its own administrators such as exchange administrators, SQL administrators, and SharePoint administrators. The other third-party applications such as CMS, billing portal may have its own administrators. If you are using cloud services, SaaS applications, it has another set of administrators. Are we really aware of activities happening on these accounts? Mostly engineers are only worrying about protecting domain admin accounts, but at the same time forgetting about the other kinds of administrators in the infrastructure. Some of these administrator roles can make more damage than domain admin to a business. These application and services are decentralizing the management in the organization. In order to move latterly with privileges, these attackers only need to log into a machine or server where these administrators used to log in.  Local Security Authority Subsystem Service(LSASS) stores credentials in its memory for active Windows sessions. This prevents users from entering credentials for each and every service they access. This also stores Kerberos tickets. This allows attackers to perform a pass of the hash attack and retrieve locally stored credentials. Decentralized management of admin accounts make this process easier.

There are features, security best practices which can be used to prevent the pass of the hash attacks in identity infrastructure. 

Another problem with these types of accounts is once it becomes service admin accounts, eventually its becomes domain admin or enterprise administrator accounts. I have seen engineers created service accounts and when they can’t figure out the exact permission required for the program, as an easy fix it will add to the domain admin group. It’s not only the infrastructure attack that can expose such credentials. Service admins are attached to the application too, compromise on application can also expose the identities. In such scenario, it will be easier for attackers to gain keys to the kingdom. 

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Tier 0 is where the domain admin, enterprise admins operates. This is what the ultimate goal for identity infrastructure attack, once they obtain access to Tier 0, it means they own your entire identity infrastructure. Latest reports show once there is initial breach, it only takes less than 48 hours to gain Tier 0 privileges. According to the reports, once they gain access it will take up to 7-8 months minimum to identify the breach. Because once they have highest privileges they can make backdoors, clean up logs and hide forever if needed. Systems we use, always treat administrators as trustworthy people. It’s no longer valid statement for modern world. How many times you check systems logs to see what your domain admins are doing? Even though engineers look for the logs for other users, majority rarely check about domain admin accounts. The same thing applies for internal security breach too, as I said most people are good but you never know. Most of world famous identity attacks have proved that already.

When I have discussion with engineers and customers about identity infrastructure security, following are the common comments I hear,

  • "We have too many administrator accounts"
  • "We do not know how many administrator account we got"
  • "We got fast changing IT teams, so it’s hard to manage permissions"
  • "We do not have visibility over administrator accounts activities"
  • "If there is identity infrastructure breach or attempt, how do we identify?"

Answer for all of these is PAM. As I said in the beginning, this is not one product. It’s a workflow and a new way of working. Main components for this process is listed as follows:

  1. Apply pass-the-hash prevention features to existing identity infrastructure.
  2. Install Microsoft Advanced Threat Analytics to monitor the domain controller traffic to identify potential real-time identity infrastructure threats.
  3. Install and configure Microsoft Identity Manager 2016—this product is allowing to manage privilege access of existing Active Directory forest by providing task-based time limited privilege access. 

What is it to do with AD DS 2016?

AD DS 2016 is now allowing time based group membership which makes this whole process possible. Users will add to the groups with TTL value and once its expires, the user will be removed from the group automatically. For example, let’s assume your CRM application has administrator rights assign to CRM Admin security group. The users in this group only log into the system once a month to do some maintenance. But the admin rights for the members in that group remain untouched for 29 days—24x7. So, it gives enough opportunity for attackers to try and gain access to the privileged accounts during that time. But if it’s admin rights can be limited at least for the day it needed isn’t it more useful? Then we know majority of days in month, CRM application do not have risk of been compromised by an account in CRM Admin group.

What is the logic behind PAM?

PAM product is built, based on Just-In-Time (JIT) administration concept. Back in 2014, Microsoft release PowerShell tool kit which allows Just-Enough-Administration. Let’s assume you are running a web server in your infrastructure. As part of the operation, every month you need to collect some logs to make a report. You already setup a PowerShell script for it. Someone in your team need to log into the system and need to run it. In order to do that, it requires administration privileges. Using JEA, it is possible to assign required permissions for the user to run only that particular program. In that way, user doesn't need to be added to the domain admin group. User will not be allowed to run any other program with assigned permission and it will not apply for another computer either. JIT administration is bound with time. Users will have required privileges only when they need it. Users will not hold privileged access rights all the time.

PAM operations can be divide in to 4 major steps:

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Source -

  • Prepare: First step is to identify the privileged access groups in your exciting Active Directory forest and start to remove users from those. You may also need to do certain changes in your application infrastructure to support this setup. For example, if you assign privileged access to user accounts instead of security groups (in applications or services) it will need to change. Then next step is to setup equivalent groups in bastion forest without any members.

When setup MIM, it will use a bastion forest to manage privileged access in existing Active Directory forest. This is a special forest and it cannot use for other infrastructure operations. This forest running with minimum of Windows Server 2012 R2 Active Directory forest functional level. When identity infrastructure compromised and attackers gain access to Tier 0, they can hide their activities for months or years. How we can be sure our existing identity infrastructure is not compromised already? if we implement this to same forest it will not achieve its core targets. Also, domain upgrades are painful it need time and budget. But because of the bastion forest, this solution can be applied to your existing identity infrastructure with minimum changes. 

  • Protect: Next step is in the list to setup a workflow for authentications and authorization. Define how user can request privileges access when they are required. It can be via MIM portal or existing support portal (with integrated MIM REST API). It is possible to setup system to use Multi-Factor authentications (MFA) during this request process to prevent any unauthorized activity. Also, its important to define how the requests will be handled. It can be automatic approval or manual approval process.
  • Operate: Once privilege access request approved, the user account will be added to the security group in bastion forest. The group itself have a SID value. In both forests, the group will have exact same SID value. Therefore the application or service will not see a difference between two groups in two different forest. Once the permission is granted it is only valid for the time defined by the authorization policy. Once it reaches the time limit, the user account will be removed from the security group automatically.
  • Monitor: PAM provides visibility over the privilege access requests. Each and every request, events will be recorded and it is possible to review and also generate reports for audit purposes. It helps to fine tune the process and also to identify potential threats. 

Let’s see how it’s really works:

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REBELADMIN CORP. uses a CRM system for its operations. The application got administrator role and REBELADMIN/CRMAdmins security group assigned to it. Any member of that group will have administrator privileges to the application. Recently PAM been introduced to the REBELADMIN CORP. As an engineer, I have identified REBELADMIN/CRMAdmins as privileged group and going to protect it using PAM. The first step is to remove the members of the REBELADMIN/CRMAdmins group. After that I have setup same group in the bastion forest. Not only the name is same, but also both the groups got the same SID value 1984. 

User Dennis used to be a member of the REBELADMIN/CRMAdmins group and was running monthly report. At the end of the month, he tried to run it and now figured he do not have the required permissions. Next step for him is to request the required permission via MIM Portal. According to the policies, as part of the request, system wants Dennis to use MFA. Once Dennis verifies the PIN number the request logs in the portal. As administrator, I received the alert about the request and I log into system to review the request. It's legitimate request and I approve his access to the system for 8 hours. Then the system automatically added the user account for Dennis into BASTION/CRMAdmins group. This group have the same SID value as the production group. Therefore, the member of BASTION/CRMAdmins group will be treated as administrator by CRM application. This group membership contains TTL value too. After it passes 8 hours from approval, Dennis’s account will be automatically removed from BASTION/CRMAdmins group. In this process, we didn’t add any member to the production security group which is REBELADMIN/CRMAdmins. So, production forest stay untouched and protected.

In here the most important thing we need to understand is the legacy approach for identity protection is no longer valid. We are against human adversaries. Identity is our new perimeter in infrastructure and to protect it we need to understand how adversaries doing it and stay step ahead. The new PAM with AD DS 2016 is new approach to the right direction. 

Time based group memberships

Time based group membership is part of that boarder topic. This allows administrators to assign temporarily group membership which is expressed by Time-To-Live (TTL) value. This value will add to the Kerberos ticket. This is also called as Expiring-Link feature. When a user is assigned to a temporarily group membership, his login Kerberos ticket granting ticket (TGT) life time will be equal to lowest TTL value he has. For example, let’s assume you granted temporarily group membership to user A to be a member of domain admin group. It is only valid for 60 minutes. But user logged in only after 50 minutes from original assign and only have 10 minutes left to be a member of domain admin group. Based on that domain controller will issue TGT only valid for 10 minutes for user A. 

This feature is not enabled by default. The reason for that is, to use this feature the forest function level must be Windows Server 2016. Also, once this feature is enabled, it cannot be disabled. 

Let’s see how it works in real world:

  1. I have Windows domain controller installed and it is running with Windows Server 2016 forest functional level. It can be verified using the following PowerShell command:
    Get-ADForest | fl Name,ForestMode
  2. Then we need to enable the Expiring Link feature. It can be enabled using the following command:

    Enable-ADOptionalFeature ‘Privileged Access Management Feature’ -Scope
    ForestOrConfigurationSet -Target
  3. The link can be replaced with your FQDN:

     Mastering Active Directory

  4. I have a user called Adam Curtiss to whom I need to assign Domain Admins group membership for 60 minutes:

    Get-ADGroupMember “Domain Admins”
  5. The preceding command will list the current member of domain admin group: 

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  6. Next step is to add the user Adam Curtiss to the Domain Admins group for 60 minutes:

     Add-ADGroupMember -Identity ‘Domain Admins’ -Members ‘acurtiss’ -MemberTimeToLive (New-TimeSpan -Minutes 60)
  7.  Once its run, we can verify the TTL value remaining for the group membership using the following command: 

    Get-ADGroup ‘Domain Admins’ -Property member -ShowMemberTimeToLive

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Once I log in as the user and list the Kerberos ticket it shows the renew time with less than 60 minutes as I log in as user after few minutes of granting.

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Once the TGT renewal comes, the user will no longer be a member of Domain Admins group.


In this article we looked at the new features and enhancements that come with AD DS 2016. One of the biggest improvement was Microsoft's new approach towards the PAM. This is not just a feature that can be enabled via AD DS, it's just a part of the border solution. It helps to protect identity infrastructures from adversaries as traditional techniques and technologies no longer valid with rising threats.

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