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Testing the New Version of the Windows Security Events Connector with Azure Sentinel To-Go!

Microsoft

Jun 25, 2021

Last week, on Monday June 14th, 2021, a new version of the Windows Security Events data connector reached public preview. This is the first data connector created leveraging the new generally available Azure Monitor Agent (AMA) and Data Collection Rules (DCR) features from the Azure Monitor ecosystem. As any other new feature in Azure Sentinel, I wanted to expedite the testing process and empower others in the InfoSec community through a lab environment to learn more about it.

In this post, I will talk about the new features of the new data connector and how to automate the deployment of an Azure Sentinel instance with the connector enabled, the creation and association of DCRs and installation of the AMA on a Windows workstation. This is an extension of a blog post I wrote, last year (2020), where I covered the collection of Windows security events via the Log Analytics Agent (Legacy).

Azure Sentinel To-Go!?

Azure Sentinel2Go is an open-source project maintained and developed by the Open Threat Research community to automate the deployment of an Azure Sentinel research lab and a data ingestion pipeline to consume pre-recorded datasets. Every environment I release through this initiative is an environment I use and test while performing research as part of my role in the MSTIC R&D team. Therefore, I am constantly trying to improve the deployment templates as I cover more scenarios. Feedback is greatly appreciated.

A New Version of the Windows Security Events Connector?

According to Microsoft docs, the Windows Security Events connector lets you stream security events from any Windows server (physical or virtual, on-premises or in any cloud) connected to your Azure Sentinel workspace. After last week, there are now two versions of this connector:

Security events (legacy version): Based on the Log Analytics Agent (Usually known as the Microsoft Monitoring Agent (MMA) or Operations Management Suite (OMS) agent).
Windows Security Events (new version): Based on the new Azure Monitor Agent (AMA).

In your Azure Sentinel data connector's view, you can now see both connectors:

A New Version? What is New?

Data Connector Deployment

Besides using the Log Analytics Agent to collect and ship events, the old connector uses the Data Sources resource from the Log Analytics Workspace resource to set the collection tier of Windows security events.

The new connector, on the other hand, uses a combination of Data Connection Rules (DCR) and Data Connector Rules Association (DCRA). DCRs define what data to collect and where it should be sent. Here is where we can set it to send data to the log analytics workspace backing up our Azure Sentinel instance.

In order to apply a DCR to a virtual machine, one needs to create an association between the machine and the rule. A virtual machine may have an association with multiple DCRs, and a DCR may have multiple virtual machines associated with it.

For more detailed information about setting up the Windows Security Events connector with both Log Analytics Agent and Azure Monitor Agents manually, take a look at this document.

Data Collection Filtering Capabilities

The old connector is not flexible enough to choose what specific events to collect. For example, these are the only options to collect data from Windows machines with the old connector:

All events - All Windows security and AppLocker events.
Common - A standard set of events for auditing purposes. The Common event set may contain some types of events that aren't so common. This is because the main point of the Common set is to reduce the volume of events to a more manageable level, while still maintaining full audit trail capability.

Minimal - A small set of events that might indicate potential threats. This set does not contain a full audit trail. It covers only events that might indicate a successful breach, and other important events that have very low rates of occurrence.
None - No security or AppLocker events. (This setting is used to disable the connector.)

According to Microsoft docs, these are the pre-defined security event collection groups depending on the tier set:

On the other hand, the new connector allows custom data collection via XPath queries. These XPath queries are defined during the creation of the data collection rule and are written in the form of LogName!XPathQuery. Here are a few examples:

Collect only Security events with Event ID = 4624

Security!*[System[(EventID=4624)]]

Collect only Security events with Event ID = 4624 or Security Events with Event ID = 4688

Security!*[System[(EventID=4624 or EventID=4688)]]

Collect only Security events with Event ID = 4688 and with a process name of consent.exe.

Security!*[System[(EventID=4688)]] and *[EventData[Data[@Name=’ProcessName’]=’C:\Windows\System32\consent.exe’]]

You can select the custom option to select which events to stream:

Important!

Based on the new connector docs, make sure to query only Windows Security and AppLocker logs. Events from other Windows logs, or from security logs from other environments, may not adhere to the Windows Security Events schema and won’t be parsed properly, in which case they won’t be ingested to your workspace.

Also, the Azure Monitor agent supports XPath queries for XPath version 1.0 only. I recommend reading the Xpath 1.0 Limitation documentation before writing XPath Queries.

XPath?

XPath stands for XML (Extensible Markup Language) Path language, and it is used to explore and model XML documents as a tree of nodes. Nodes can be represented as elements, attributes, and text.

In the image below, we can see a few node examples in the XML representation of a Windows security event:

XPath Queries?

XPath queries are used to search for patterns in XML documents and leverage path expressions and predicates to find a node or filter specific nodes that contain a specific value. Wildcards such as ‘*’ and ‘@’ are used to select nodes and predicates are always embedded in square brackets “[]”.

Matching any element node with ‘*’

Using our previous Windows Security event XML example, we can process Windows Security events using the wildcard ‘*’ at the `Element` node level.

The example below walks through two ‘Element’ nodes to get to the ‘Text’ node of value ‘4688’.

You can test this basic ‘XPath’ query via PowerShell.

Open a PowerShell console as ‘Administrator’.
Use the Get-WinEvent command to pass the XPath query.
Use the ‘Logname’ parameter to define what event channel to run the query against.
Use the ‘FilterXPath’ parameter to set the XPath query.

Get-WinEvent -LogName Security -FilterXPath '*[System[EventID=4688]]

Matching any attribute node with ‘@’

As shown before, ‘Element’ nodes can contain ‘Attributes’ and we can use the wildcard ‘@’ to search for ‘Text’ nodes at the ‘Attribute’ node level. The example below extends the previous one and adds a filter to search for a specific ‘Attribute’ node that contains the following text: 'C:\Windows\System32\cmd.exe’.

Once again, you can test the XPath query via PowerShell as Administrator.

$XPathQuery = "*[System[EventID=4688]] and *[EventData[Data[@Name='ParentProcessName']='C:\Windows\System32\cmd.exe']]" 
Get-WinEvent -LogName Security -FilterXPath $XPathQuery

Can I Use XPath Queries in Event Viewer?

Every time you add a filter through the Event Viewer UI, you can also get to the XPath query representation of the filter. The XPath query is part of a QueryList node which allows you to define and run multiple queries at once.

We can take our previous example where we searched for a specific attribute and run it through the Event Viewer Filter XML UI.

<QueryList> 
    <Query Id="0" Path="Security"> 
        <Select Path="Security">*[System[(EventID=4688)]] and *[EventData[Data[@Name='ParentProcessName']='C:\Windows\System32\cmd.exe']]</Select> 
    </Query> 
</QueryList>

Now that we have covered some of the main changes and features of the new version of the Windows Security Events data connector, it is time to show you how to create a lab environment for you to test your own XPath queries for research purposes and before pushing them to production.

Deploy Lab Environment

Identify the right Azure resources to deploy.
Create deployment template.
Run deployment template.

Identify the Right Azure Resources to Deploy

As mentioned earlier in this post, the old connector uses the Data Sources resource from the Log Analytics Workspace resource to set the collection tier of Windows security events.

This is the Azure Resource Manager (ARM) template I use in Azure-Sentinel2Go to set it up:

Azure-Sentinel2Go/securityEvents.json at master · OTRF/Azure-Sentinel2Go (github.com)

Data Sources Azure Resource

{ 
  "type": "Microsoft.OperationalInsights/workspaces/dataSources", 
  "apiVersion": "2020-03-01-preview", 
  "location": "eastus", 
  "name": "WORKSPACE/SecurityInsightsSecurityEventCollectionConfiguration", 
  "kind": "SecurityInsightsSecurityEventCollectionConfiguration", 
  "properties": { 
    "tier": "All", 
    "tierSetMethod": "Custom" 
  } 
}

However, the new connector uses a combination of Data Connection Rules (DCR) and Data Connector Rules Association (DCRA).

This is the ARM template I use to create data collection rules:

Azure-Sentinel2Go/creation-azureresource.json at master · OTRF/Azure-Sentinel2Go (github.com)

Data Collection Rules Azure Resource

{ 
  "type": "microsoft.insights/dataCollectionRules", 
  "apiVersion": "2019-11-01-preview", 
  "name": "WindowsDCR", 
  "location": "eastus", 
  "tags": { 
    "createdBy": "Sentinel" 
  }, 
  "properties": { 
    "dataSources": { 
      "windowsEventLogs": [ 
        { 
          "name": "eventLogsDataSource", 
          "scheduledTransferPeriod": "PT5M", 
          "streams": [ 
            "Microsoft-SecurityEvent" 
          ], 
          "xPathQueries": [ 
            "Security!*[System[(EventID=4624)]]" 
          ] 
        } 
      ] 
    }, 
    "destinations": { 
      "logAnalytics": [ 
        { 
          "name": "SecurityEvent", 
          "workspaceId": "AZURE-SENTINEL-WORKSPACEID", 
          "workspaceResourceId": "AZURE-SENTINEL-WORKSPACERESOURCEID" 
        } 
      ] 
    }, 
    "dataFlows": [ 
      { 
        "streams": [ 
          "Microsoft-SecurityEvent" 
        ], 
        "destinations": [ 
          "SecurityEvent" 
        ] 
      } 
    ] 
  } 
}

One additional step in the setup of the new connector is the association of the DCR with Virtual Machines.

This is the ARM template I use to create DCRAs:

Azure-Sentinel2Go/association.json at master · OTRF/Azure-Sentinel2Go (github.com)

Data Collection Rule Associations Azure Resource

{
  "name": "WORKSTATION5/microsoft.insights/WindowsDCR", 
"type": "Microsoft.Compute/virtualMachines/providers/dataCollectionRuleAssociations", 
  "apiVersion": "2019-11-01-preview", 
  "location": "eastus", 
   "properties": { 
"description": "Association of data collection rule. Deleting this association will break the data collection for this virtual machine.", 
    "dataCollectionRuleId": "DATACOLLECTIONRULEID" 
   } 
}

What about the XPath Queries?

As shown in the previous section, the XPath query is part of the “dataSources” section of the data collection rule resource. It is defined under the ‘windowsEventLogs’ data source type.

"dataSources": { 
  "windowsEventLogs": [ 
    { 
      "name": "eventLogsDataSource", 
      "scheduledTransferPeriod": "PT5M", 
      "streams": [ 
        "Microsoft-SecurityEvent" 
      ], 
      "xPathQueries": [ 
        "Security!*[System[(EventID=4624)]]" 
      ] 
    } 
  ] 
}

Create Deployment Template

We can easily add all those ARM templates to an ‘Azure Sentinel & Win10 Workstation’ basic template. We just need to make sure we install the Azure Monitor Agent instead of the Log Analytics one, and enable the system-assigned managed identity in the Azure VM.

Template Resource List to Deploy:

Azure Sentinel Instance
Windows Virtual Machine
Azure Monitor Agent Installed.
System-assigned managed identity Enabled.
Data Collection Rule
Log Analytics Workspace ID
Log Analytics Workspace Resource ID
Data Collection Rule Association
Data Collection Rule ID
Windows Virtual Machine Resource Name

The following ARM template can be used for our first basic scenario:

Azure-Sentinel2Go/Win10-DCR-AzureResource.json at master · OTRF/Azure-Sentinel2Go (github.com)

Run Deployment Template

You can deploy the ARM template via a “Deploy to Azure” button or via Azure CLI.

“Deploy to Azure” Button

Browse to Azure Sentinel2Go repository
Go to grocery-list/Win10/demos.
Click on the “Deploy to Azure” button next to “Azure Sentinel + Win10 + DCR (DCR Resource)”
Fill out the required parameters:
- adminUsername: admin user to create in the Windows workstation.
- adminPassword: password for admin user.
- allowedIPAddresses: Public IP address to restrict access to the lab environment.
Wait 5-10 mins and your environment should be ready.

Azure CLI

Download demo template.
Open a terminal where you can run Azure CLI from (i.e. PowerShell).
Log in to your Azure Tenant locally.
```
az login 
```

Create Resource Group (Optional)

az group create -n AzSentinelDemo -l eastus

Deploy ARM template locally.

az deployment group create –f ./ Win10-DCR-AzureResource.json -g MYRESOURCRGROUP –adminUsername MYUSER –adminPassword MYUSERPASSWORD –allowedIPAddresses x.x.x.x

Wait 5-10 mins and your environment should be ready.

Whether you use the UI or the CLI, you can monitor your deployment by going to Resource Group > Deployments:

Verify Lab Resources

Once your environment is deployed successfully, I recommend verifying every resource that was deployed.

Azure Sentinel New Data Connector

You will see the Windows Security Events (Preview) data connector enabled with a custom Data Collection Rules (DCR):

If you edit the custom DCR, you will see the XPath query and the resource that it got associated with. The image below shows the association of the DCR with a machine named workstation5.

You can also see that the data collection is set to custom and, for this example, we only set the event stream to collect events with Event ID 4624.

Windows Workstation

I recommend to RDP to the Windows Workstation by using its Public IP Address. Go to your resource group and select the Azure VM. You should see the public IP address to the right of the screen. This would generate authentication events which will be captured by the custom DCR associated with the endpoint.

Check Azure Sentinel Logs

Go back to your Azure Sentinel, and you should start seeing some events on the Overview page:

Go to Logs and run the following KQL query:

SecurityEvent 
| summarize count() by EventID

As you can see in the image below, only events with Event ID 4624 were collected by the Azure Monitor Agent.

You might be asking yourself, “Who would only want to collect events with Event ID 4624 from a Windows endpoint?”. Believe it or not, there are network environments where due to bandwidth constraints, they can only collect certain events. Therefore, this custom filtering capability is amazing and very useful to cover more use cases and even save storage!

Any Good XPath Queries Repositories in the InfoSec Community?

Now that we know the internals of the new connector and how to deploy a simple lab environment, we can test multiple XPath queries depending on your organization and research use cases and bandwidth constraints. There are a few projects that you can use.

Palantir WEF Subscriptions

One of many repositories out there that contain XPath queries is the ‘windows-event-forwarding' project from Palantir. The XPath queries are Inside of the Windows Event Forwarding (WEF) subscriptions. We could take all the subscriptions and parse them programmatically to extract all the XPath queries saving them in a format that can be used to be part of the automatic deployment.

You can run the following steps in this document available in Azure Sentinel To-go and extract XPath queries from the Palantir project.

Azure-Sentinel2Go/README.md at master · OTRF/Azure-Sentinel2Go (github.com)

OSSEM Detection Model + ATT&CK Data Sources

From a community perspective, another great resource you can use to extract XPath Queries from is the Open Source Security Event Metadata (OSSEM) Detection Model (DM) project. A community driven effort to help researchers model attack behaviors from a data perspective and share relationships identified in security events across several operating systems.

One of the use cases from this initiative is to map all security events in the project to the new ‘Data Sources’ objects provided by the MITRE ATT&CK framework. In the image below, we can see how the OSSEM DM project provides an interactive document (.CSV) for researchers to explore the mappings (Research output):

One of the advantages of this project over others is that all its data relationships are in YAML format which makes it easy to translate to others formats. For example, XML. We can use the Event IDs defined in each data relationship documented in OSSEM DM and create XML files with XPath queries in them.

Exploring OSSEM DM Relationships (YAML Files)

Let’s say we want to use relationships related to scheduled jobs in Windows.

Translate YAML files to XML Query Lists

We can process all the YAML files and export the data in an XML files. One thing that I like about this OSSEM DM use case is that we can group the XML files by ATT&CK data sources. This can help organizations organize their data collection in a way that can be mapped to detections or other ATT&CK based frameworks internally.

We can use the QueryList format to document all 'scheduled jobs relationships' XPath queries in one XML file.

I like to document my XPath queries first in this format because it expedites the validation process of the XPath queries locally on a Windows endpoint. You can use that XML file in a PowerShell command to query Windows Security events and make sure there are not syntax issues:

[xml]$scheduledjobs = get-content .\scheduled-job.xml
Get-WinEvent -FilterXml $scheduledjobs

Translate XML Query Lists to DCR Data Source:

Finally, once the XPath queries have been validated, we could simply extract them from the XML files and put them in a format that could be used in ARM templates to create DCRs. Do you remember the dataSources property of the DCR Azure resource we talked about earlier? What if we could get the values of the windowsEventLogs data source directly from a file instead of hardcoding them in an ARM template? The example below is how it was previously being hardcoded.

"dataSources": { 
  "windowsEventLogs": [ 
    { 
      "name": "eventLogsDataSource", 
      "scheduledTransferPeriod": "PT5M", 
      "streams": [ 
        "Microsoft-SecurityEvent" 
      ], 
      "xPathQueries": [ 
        "Security!*[System[(EventID=4624)]]" 
      ] 
    } 
  ] 
}

We could use the XML files created after processing OSSEM DM relationships mapped to ATT&CK data sources and creating the following document. We can pass the URL of the document as a parameter in an ARM template to deploy our lab environment:

Azure-Sentinel2Go/ossem-attack.json at master · OTRF/Azure-Sentinel2Go (github.com)

Wait! How Do You Create the Document?

The OSSEM team is contributing and maintaining the JSON file from the previous section in the Azure Sentinel2Go repository. However, if you want to go through the whole process on your own, Jose Rodriguez (@Cyb3rpandah) was kind enough to write every single step to get to that output file in the following blog post:

OSSEM Detection Model: Leveraging Data Relationships to Generate Windows Event XPath Queries (openthreatresearch.com)

Ok, But, How Do I Pass the JSON file to our Initial ARM template?

In our initial ARM template, we had the XPath query as an ARM template variable as shown in the image below.

We could also have it as a template parameter. However, it is not flexible enough to define multiple DCRs or even update the whole DCR Data Source object (Think about future coverage beyond Windows logs).

Data Collection Rules – CREATE API

For more complex use cases, I would use the DCR Create API. This can be executed via a PowerShell script which can also be used inside of an ARM template via deployment scripts. Keep in mind that, the deployment script resource requires an identity to execute the script. This managed identity of type user-assigned can be created at deployment time and used to create the DCRs programmatically.

PowerShell Script

If you have an Azure Sentinel instance without the data connector enabled, you can use the following PowerShell script to create DCRs in it. This is good for testing and it also works in ARM templates.

Keep in mind, that you would need to have a file where you can define the structure of the windowsEventLogs data source object used in the creation of DCRs. We created that in the previous section remember? Here is where we can use the OSSEM Detection Model XPath Queries File 😉

Azure-Sentinel2Go/ossem-attack.json at master · OTRF/Azure-Sentinel2Go (github.com)

FileExample.json

{ 
  "windowsEventLogs":  [ 
    { 
      "Name":  "eventLogsDataSource", 
      "scheduledTransferPeriod":  "PT1M", 
      "streams":  [ 
        "Microsoft-SecurityEvent" 
      ], 
      "xPathQueries":  [ 
        "Security!*[System[(EventID=5141)]]", 
        "Security!*[System[(EventID=5137)]]", 
        "Security!*[System[(EventID=5136 or EventID=5139)]]", 
        "Security!*[System[(EventID=4688)]]", 
        "Security!*[System[(EventID=4660)]]", 
        "Security!*[System[(EventID=4656 or EventID=4661)]]", 
        "Security!*[System[(EventID=4670)]]" 
       ] 
    } 
  ] 
}

Run Script

Once you have a JSON file similar to the one in the previous section, you can run the script from a PowerShell console:

.\Create-DataCollectionRules.ps1 -WorkspaceId xxxx -WorkspaceResourceId xxxx -ResourceGroup MYGROUP -Kind Windows -DataCollectionRuleName WinDCR -DataSourcesFile FileExample.json -Location eastus –verbose

One thing to remember is that you can only have 10 Data Collection rules. That is different than XPath queries inside of one DCR. If you attempt to create more than 10 DCRs, you will get the following error message:

ERROR 

VERBOSE: @{Headers=System.Object[]; Version=1.1; StatusCode=400; Method=PUT;  
Content={"error":{"code":"InvalidPayload","message":"Data collection rule is invalid","details":[{"code":"InvalidProperty","message":"'Data Sources. Windows Event Logs' item count should be 10 or less. Specified list has 11 items.","target":"Properties.DataSources.WindowsEventLogs"}]}}}

Also, if you have duplicate XPath queries in one DCR, you would get the following message:

ERROR
VERBOSE: @{Headers=System.Object[]; Version=1.1; StatusCode=400; Method=PUT;  
Content={"error":{"code":"InvalidPayload","message":"Data collection rule is invalid","details":[{"code":"InvalidDataSource","message":"'X Path Queries' items must be unique (case-insensitively).  
 
Duplicate names: 
Security!*[System[(EventID=4688)]],Security!*[System[(EventID=4656)]].","target":"Properties.DataSources.WindowsEventLogs[0].XPathQueries"}]}}}

ARM Template: DeploymentScript Resource

Now that you know how to use a PowerShell script to create DCRs directly to your Azure Sentinel instance, we can use it inside of an ARM template and make it point to the JSON file that contains all the XPath queries in the right format contributed by the OSSEM DM project.

This is the template I use to put it all together:

Azure-Sentinel2Go/Win10-DCR-DeploymentScript.json at master · OTRF/Azure-Sentinel2Go (github.com)

What about the DCR Associations?

You still need to associate the DCR with a virtual machine. However, we can keep doing that within the template leveraging the DCRAs Azure resource linked template inside of the main template. Just in case you were wondering how I call the linked template from the main template, I do it this way:

Azure-Sentinel2Go/Win10-DCR-DeploymentScript.json at master · OTRF/Azure-Sentinel2Go (github.com)

How Do I Deploy the New Template?

The same way how we deployed the initial one. If you want the Easy Button , then simply browse to the URL below and click on the blue button highlighted in the image below:

Link: Azure-Sentinel2Go/grocery-list/Win10/demos at master · OTRF/Azure-Sentinel2Go (github.com)

Wait 5-10 mins!

Enjoy it!

That’s it! You now know two ways to deploy and test the new data connector and Data Collection Rules features with XPath queries capabilities. I hope this was useful. Those were all my notes while testing and developing templates to create a lab environment so that you could also expedite the testing process!

Feedback is greatly appreciated! Thank you to the OSSEM team and the Open Threat Research (OTR) community for helping us operationalize the research they share with the community! Thank you, Jose Rodriguez.

Demo Links

References

Cyb3rWard0g

Microsoft

Joined March 23, 2020

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