Category Archives: PowerShell

Bringing up a new Active Directory Domain Series (Server 2022) [Part 1]

Change ms-DS-MachineAccountQuota to Zero

This attribute allows all users in the Domain to bind 10 computer objects to the Domain that they control. This could actually lead to more than 10 computer objects since every computer object is also technically a user. Best practices is to disable this setting and set it to Zero.

You can run the following command to see if your domain is currently configured as default of 10 objects:

Get-ADObject -Identity ((Get-ADDomain).distinguishedName) -Properties ms-DS-MachineAccountQuota

If you are currently set to 10 and want to fall in line with best practices you can run the following command to change this attribute to Zero:

Set-ADDomain -Identity ((Get-ADDomain).distinguishedName) -Replace @{“ms-DS-MachineAccountQuota”=”0”}

You will not be provided any feedback, you can then run the first command again to verify things are set to Zero.

Enable Recycle Bin

To enable the Recycle Bin you can run the following command (Replace DOMAIN.COM and make sure quotes copy):

Enable-ADOptionalFeature -Identity “CN=Recycle Bin Feature,CN=Optional Features,CN=Directory Service,CN=Windows NT,CN=Services,CN=Configuration,DC=DOMAIN,DC=COM” -Scope ForestOrConfigurationSet -Target “DOMAIN.COM“

Create Key for gMSA Accounts

When you bring up a new domain you will need to create the KDSRootKey for group managed service accounts.

Add-KdsRootKey -EffectiveImmediately

KDS root keys are stored in: CN=Master Root Keys,CN=Group Key Distribution Service,CN=Services,CN=Configuration,DC=<forest name>;

Enable Central Store in Group Policy

Create the “PolicyDefinitions” folder in SYSVOL

Once enabled, copy the files from C:\Windows\PolicyDefinitions into this folder

Install & Configure LAPS

You can verify you have the AD Schema updated for LAPS by running:

Update-LapsADSchema

You can verify that the LAPS GPOs are in Computer Configuration > Administrative Templates > System > LAPS

Create Group Policy Security Baseline for Domain Controllers

Download the Windows Server 2022 Security Baseline from Microsoft: https://www.microsoft.com/en-us/download/details.aspx?id=55319

Copy these files to a Domain Controller for example in C:\Temp

Copy the files from \Templates directory into the PolicyDefinitions folder in SYSVOL

In the \Scripts directory run the .\Baseline-ADImport.ps1 file to import the GPOs

Modify the firewall rules to enforce only the rules you specify:

Turn off Rule Merging for all profiles
Turn on firewall log with max size 32,767 for all profiles
Log dropped and successful packets for all profiles
Input Firewall Rules
- ICMP (Ping Allow)
- TCP/UDP 53 (DNS)
- TCP/UDP 88 (Kerberos)
- UDP 123 (Time Service)
- TCP/UDP 135 (RPC Mapper)
- TCP/UDP 389 (LDAP)
- TCP 445 (SMB)
- TCP/UDP 464 (Kerberos Password Change)
- TCP 636 (LDAPS)
- TCP 3268/3269 (Global Catalog)
- TCP 49152-65535 (RPC Dynamic Range) [Will modify this later]
- TCP/UDP 3389 (RDP) [Locked to Trusted IPs]
- TCP 5985/5986 (WinRM) [Locked to Trusted IPs]
- TCP 9389 (AD Web Services) [Locked to Trusted IPs]

Manually create the firewall logs on the DCs by launching Windows Defender Firewall, Go to the Log Settings and click “OK”

Create Another GPO or Add These Settings to the Current GPO

Navigate to Computer Configuration > Policies > Windows Settings > Security Settings > System Services > Print Spooler

Define this policy and set the service startup mode to Disabled

Navigate to Computer Configuration > Preferences > Windows Settings > Registry (Use Update HKLM)

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\Triple DES 168\Enabled 0

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\SSL 3.0\Server\Enabled 0

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\TLS 1.0\Server\Enabled 0

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\TLS 1.1\Server\Enabled 0

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\TLS 1.2\Server\DisabledByDefault 0

SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\TLS 1.2\Server\Enabled 1

Things to check when taking over an Active Directory Domain

This blog is a work in progress but I will be keeping track of things to check when taking over an Active Directory Domain. This is not an all inclusive list but a list of common things to check.

ms-DS-MachineAccountQuota

By default in Active Directory this value is set to “10” which allows ANY user in Active Directory to bind ten machines to the domain. In the beginning stages of Active Directory maybe there was a need for this but now its just a big security risk.

Recommendation: Set this to zero

Protected Users Group

Look at highly privileged accounts and add them to the Protected Users Group if they are compatible with the protections that this group provides.

Recommendation: Add any real user accounts that are at Domain Admin or higher. (Enterprise Admins, Schema Admins, etc.)

krbtgt Account Password

Check the last time this password was changed and if it wasn’t changed in the last 180 days, change it.

Recommendation: Make sure you setup a schedule to recycle this password twice a year. This account holds two passwords so when you change the password you should change it twice, ideally 24 hours apart. That is a total of four password changes a year.

Verify SSL Certificates Exist on the Domain Controllers

Verify that valid certificates are in place for LDAPS calls over port 636. As part of this process investigate and try to remove any traffic that is talking on LDAP port 389.

Recommendation: Use either an internal PKI or public facing certificates to make sure all ldaps traffic is talking Active Directory over a secure connection.

Check if Exchange ExtensionAttributes were installed

If “ExtensionAttribute1” -> “ExtensionAttribute15” are in the schema of User/Computer/Group objects, check to see if any of them are in use.

Recommendation: If they are try to document what they are being used for and which ones are free and able to be used.

Check the Default Computer/User Bind OU

The default container for computer objects is (CN=Computers,DC=DOMAIN,DC=COM). This container cannot have group policy applied to it and objects should be set to write to another OU that can be better managed.

Excerpt from Microsoft here: Redirect users and computers containers – Windows Server | Microsoft Learn

“In a default installation of an Active Directory domain, user, computer, and group accounts are put in CN=objectclass containers instead of a more desirable OU class container. Similarly, the accounts that were created by using earlier-version APIs are put in the CN=Users and CN=computers containers.”

“Some applications require specific security principals to be located in default containers like CN=Users or CN=Computers. Verify that your applications have such dependencies before you move them out of the CN=users and CN=computes containers.”

Recommendation: If these items can be re-directed, redirect them to a different OU and make sure proper OU security is set.

Check Tombstone Lifetime / AD Recycle Bin

If the Active Directory Recycle Bin is not enabled, enable it!

The following PowerShell code can be used to see what the current Tombstone Lifetime is:

Write-Output “Get Tombstone Setting `r” Import-Module ActiveDirectory $ADForestconfigurationNamingContext = (Get-ADRootDSE).configurationNamingContext $DirectoryServicesConfigPartition = Get-ADObject -Identity “CN=Directory Service,CN=Windows NT,CN=Services,$ADForestconfigurationNamingContext” -Partition $ADForestconfigurationNamingContext -Properties * $TombstoneLifetime = $DirectoryServicesConfigPartition.tombstoneLifetime Write-Output “Active Directory’s Tombstone Lifetime is set to $TombstoneLifetime days `r “

Note that no value returned means the tombstone lifetime setting is set to 60 days (default for AD forests installed with Windows 2003 or older).

Recommendation: If it is not set to 180 days, set it to 180 days. If the AD recycle bin is not enabled, enable it!

Check to see if Sysmon is installed on the Domain Controllers

Recommendation: If Sysmon is not installed, work on getting it installed and configured on the Domain Controllers at a bare minimum

Check Domain Controller Firewall Settings

This may require a conversation with your Information Security team to understand how the Firewalls are configured that sit in front of the Domain Controllers. You want to make sure the bare minimum number of ports are enabled for client traffic and that admin ports are only able to be accessed by admins.

Recommendation: Review security with Information Security Team, and enable the Windows Firewall on all Domain Controllers and manage it with Group Policy. This also acts as an East/West traffic block so if someone gets into one server on the prod network they don’t automatically have RDP access per say to another DC on the same network segment. Setup monitoring for any RDP sessions, successful ones, and failures (including firewall logs). This will verify anyone RDP’ing to the DCs is legit, and will also help track down threat actors on the network. One of the first things threat actors will try to do is see if they have RDP access to the Domain Controllers, this is good information to send to the SOC or InfoSec.

Check to see if RPC Ports are restricted

Recommendation: If RPC Ports have not been limited on the Domain Controllers, limit them to a few ports, say 100, or 1,000, and then make the associated changes to firewall rules.

Check Time Settings on the Domain Controller running PDC Emulator

Many people know that the clients that talk to the Domain Controllers have to have the correct time, but it is super important that you are pulling a correct time source for your Domain Controllers.

Recommendation: Make sure the Domain Controllers, more specifically the Domain Controller with the PDC FSMO role is pulling its time from a trusted source. It might also be worth writing a script to monitor this as well.

Verify FSMO Role Holder(s), Global Catalog Servers, & Backups

Verify who is running the FSMO roles for your Domain(s). Make all DCs a Global Catalog if you have a single-domain forest. Verify how AD is being backed up.

Recommendation: Depending on your specific situation you may not be able to run all FSMO roles on one DC. In my jobs I have been able to. This allows you to target this DC as the DC to be backed up, snapshotted, etc. If you are running a single-domain forest, make sure all DCs are a global catalog.

Check Trusts

Check to see if there are any trusts configured for the domain.

Recommendation: If there are any trusts, figure out if they are still needed, and make sure there is documentation on why these trusts are setup and when they can be unconfigured.

Check Sites & Services for IP Configuration

Check AD Sites & Services for configuration of IP ranges. Make yourself familiar with how this setup and why it is setup the way it is.

Recommendation: Take notes on if Sites & Services is being used. If it is being used understand the network ranges and why it is configured the way it is. If priority is being given, understand why.

Automating Windows Server Patching with SCCM and Custom PowerShell Scripts

One of my major tasks when I started my new job was to automate our Windows Server patching so I wouldn’t have to be up two nights every month to deal with patching.

All of our Windows Servers have SCCM clients on them, and we manage the patching software push and the maintenance windows for the servers to reboot with MECM. These servers are members of AD groups that are used to correlate to Device Collection in MECM. This is important because these same AD groups are used for custom scripts below.

This blog is not going to go over approving and downloading patches, setting maintenance windows, or deployment settings.

Things Done Before Automated Patch Run:

We set the Installation Deadline of patches to 2 hours before the Maintenace window (reboot).
We run a custom script on all boxes through SCCM before patching to clear the CCM Cache folder. This helps prevent running out of storage space in Windows. Our OS disks are not very big.
Set the Maintenance Schedule in Operations Manager (SCOM), so the boxes will not report issues during the patch window.
Set the custom scripts on our scripting server to force patch installs and check services.
Set time aside to manually patch the boxes that cannot be automated (i.e. Domain Controllers, etc.)

Custom Scripts For Patching:

These two scripts are pinned in Task Scheduler and uses and an AD Service account that has local admin on the servers. (This is not meant for Domain Controllers, DA would be needed).

A template for the script we use to force servers to install patches is located here:

Windows-Servers/Force_MECM_Patch_Install.ps1 at main · paularquette/Windows-Servers (github.com)

This script will basically make sure that the servers start installing patches at the time we have it run in Task Scheduler from our scripting server (Typically a few minutes after the 2 hours prior that we schedule). This requires WinRM ports open from the scripting server to the server endpoints that are being updated.

A template for the script we use to monitor the patch deployment, force MECM check-in and auto start services is here:

Windows-Servers/MECM_Patch_Monitoring.ps1 at main · paularquette/Windows-Servers (github.com)

This script we schedule to run about 20 minutes after the maintenance window starts and have it continue to run every 20 minutes until the maintenance window completes. This is a LOT of e-mails and I have not edited the script yet to just write to a log file but that would be easy enough to do. This script will report back last boot, and any attempts to either force SCCM check-in, or restart any services that failed to start.

By default if the box restarted over 25 minutes ago but not over 4 hours ago it will force an MECM check-in so the patch compliance report the next morning is accurate.

By default if the box restarted over 25 minutes ago but not over 4 hours ago, any Automatic services that are not started will be attempted to be restarted. Services can be whitelisted, so the script does not act on them.

Screenshot of Last Boot Report:

Screenshot of Services Not Started Report:

Creating Quick E-mail Reports From PowerShell

One of the tasks as a Sysadmin you may need or want to do is kick out an e-mail with data that you have written in PowerShell.

I find myself doing this a lot in my day job as more tasks get automated but you still need reporting on what is happening.

I have created an E-mail Report Template that is the basis for what I use when I need to kick out e-mail reports.

You can find this template on my github here: https://github.com/paularquette/Active-Directory/blob/main/Email_Report_Template

How To Use The Script:

If you want to iterate through data, I’m using $Var3 in this template for that purpose. You can see under Global Variables & Input Files I’m creating an empty array for $Var3 ($Var3 = @())

To see this script work, you would just need to have data to iterate through and add it to a PSObject as you can see in my commented out line under “Start Script Programming”

For Example:

ForEach ($i in $computers)
{
     $computername = $i.name
     $OULocation = $i.ou
     $Var3 += New-Object PSObject -Property @{ComputerName=$computername;Location=$OULocation}
}

You can then set out your sorting of the variable for the e-mail script, which you will see commented out in the Email Section.