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Stream and filter data from Windows DNS servers with the AMA connector

  • Artikkeli

This article describes how to use the Azure Monitor Agent (AMA) connector to stream and filter events from your Windows Domain Name System (DNS) server logs. You can then deeply analyze your data to protect your DNS servers from threats and attacks. The AMA and its DNS extension are installed on your Windows Server to upload data from your DNS analytical logs to your Microsoft Sentinel workspace.

DNS is a widely used protocol, which maps between host names and computer readable IP addresses. Because DNS wasn’t designed with security in mind, the service is highly targeted by malicious activity, making its logging an essential part of security monitoring. Some well-known threats that target DNS servers include DDoS attacks targeting DNS servers, DNS DDoS Amplification, DNS hijacking, and more.

While some mechanisms were introduced to improve the overall security of this protocol, DNS servers are still a highly targeted service. Organizations can monitor DNS logs to better understand network activity, and to identify suspicious behavior or attacks targeting resources within the network. The Windows DNS Events via AMA connector provides this type of visibility. For example, use the connector to identify clients that try to resolve malicious domain names, view and monitor request loads on DNS servers, or view dynamic DNS registration failures.

Note

The Windows DNS Events via AMA connector currently supports analytic event activities only.

Prerequisites

Before you begin, verify that you have:

  • A Log Analytics workspace enabled for Microsoft Sentinel.
  • The Windows Server DNS solution installed on your workspace.
  • Windows Server 2012 R2 with auditing hotfix and later.
  • A Windows DNS Server.

To collect events from any system that isn't an Azure virtual machine, ensure that Azure Arc is installed. Install and enable Azure Arc before you enable the Azure Monitor Agent-based connector. This requirement includes:

  • Windows servers installed on physical machines
  • Windows servers installed on on-premises virtual machines
  • Windows servers installed on virtual machines in non-Azure clouds

Configure the Windows DNS over AMA connector via the portal

Use the portal setup option to configure the connector using a single Data Collection Rule (DCR) per workspace. Afterwards, use advanced filters to filter out specific events or information, uploading only the valuable data you want to monitor, reducing costs and bandwidth usage.

If you need to create multiple DCRs, use the API instead. Using the API to create multiple DCRs will still show only one DCR in the portal.

To configure the connector:

  1. In Microsoft Sentinel, open the Data connectors page, and locate the Windows DNS Events via AMA connector.

  2. Towards the bottom of the side pane, select Open connector page.

  3. In the Configuration area, select Create data collection rule. You can create a single DCR per workspace.

    The DCR name, subscription, and resource group are automatically set based on the workspace name, the current subscription, and the resource group the connector was selected from. For example:

    Screenshot of creating a new D C R for the Windows D N S over A M A connector.

  4. Select the Resources tab > Add Resource(s).

  5. Select the VMs on which you want to install the connector to collect logs. For example:

    Screenshot of selecting resources for the Windows D N S over A M A connector.

  6. Review your changes and select Save > Apply.

Configure the Windows DNS over AMA connector via API

Use the API setup option to configure the connector using multiple DCRs per workspace. If you'd prefer to use a single DCR, use the portal option instead.

Using the API to create multiple DCRs still shows only one DCR in the portal.

Use the following example as a template to create or update a DCR:

Request URL and header 


PUT 

    https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Insights/dataCollectionRules/{dataCollectionRuleName}?api-version=2019-11-01-preview

Request body


{
    "properties": {
        "dataSources": {
            "windowsEventLogs": [],
            "extensions": [
                {
                    "streams": [
                        "Microsoft-ASimDnsActivityLogs"
                    ],
                    "extensionName": "MicrosoftDnsAgent",
                    "extensionSettings": {
                        "Filters": [
                            {
                                "FilterName": "SampleFilter",
                                "Rules": [
                                    {
                                        "Field": "EventOriginalType",
                                        "FieldValues": [
                                            "260"
                                        ]
                                    }
                                ]
                            }
                        ]
                    },
                    "name": "SampleDns"
                }
            ]
        },
        "destinations": {
            "logAnalytics": [
                {
                    "workspaceResourceId": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroup}/providers/Microsoft.OperationalInsights/workspaces/{sentinelWorkspaceName}",
                    "workspaceId": {WorkspaceGuid}",
                    "name": "WorkspaceDestination"
                }
            ]
        },
        "dataFlows": [
            {
                "streams": [
                    "Microsoft-ASimDnsActivityLogs"
                ],
                "destinations": [
                    " WorkspaceDestination "
                ]
            }
        ],
    },
    "location": "eastus2",
    "tags": {},
    "kind": "Windows",
    "id":"/subscriptions/{subscriptionId}/resourceGroups/{resourceGroup}/providers/Microsoft.Insights/dataCollectionRules/{workspaceName}-microsoft-sentinel-asimdnsactivitylogs ",
    "name": " {workspaceName}-microsoft-sentinel-asimdnsactivitylogs ",
    "type": "Microsoft.Insights/dataCollectionRules",
}

Use advanced filters in your DCRs

DNS server event logs can contain a huge number of events. We recommend using advanced filtering to filter out unneeded events before the data is uploaded, saving valuable triage time and costs. The filters remove the unneeded data from the stream of events uploaded to your workspace, and are based on a combination of multiple fields.

For more information, see Available fields for filtering.

Create advanced filters via the portal

Use the following procedure to create filters via the portal. For more information about creating filters with the API, see Advanced filtering examples.

To create filters via the portal:

  1. On the connector page, in the Configuration area, select Add data collection filters.

  2. Enter a name for the filter and select the filter type, which is a parameter that reduces the number of collected events. Parameters are normalized according to the DNS normalized schema. For more information, see Available fields for filtering.

    Screenshot of creating a filter for the Windows D N S over A M A connector.

  3. Select the values for which you want to filter the field from among the values listed in the drop-down.

    Screenshot of adding fields to a filter for the Windows D N S over A M A connector.

  4. To add complex filters, select Add exclude field to filter and add the relevant field.

    • Use comma-separated lists to define multiple values for each field.
    • To create compound filters, use different fields with an AND relation.
    • To combine different filters, use an OR relation between them.

    Filters also support wildcards as follows:

    • Add a dot after each asterisk (*.).
    • Don't use spaces between the list of domains.
    • Wildcards apply to the domain's subdomains only, including www.domain.com, regardless of the protocol. For example, if you use *.domain.com in an advanced filter:
      • The filter applies to www.domain.com and subdomain.domain.com, regardless of whether the protocol is HTTPS, FTP, and so on.
      • The filter doesn't apply to domain.com. To apply a filter to domain.com, specify the domain directly, without using a wildcard.

  5. To add more new filters, select Add new exclude filter.

  6. When you're finished adding filters, select Add.

  7. Back on the main connector page, select Apply changes to save and deploy the filters to your connectors. To edit or delete existing filters or fields, select the edit or delete icons in the table under the Configuration area.

  8. To add fields or filters after your initial deployment, select Add data collection filters again.

Advanced filtering examples

Use the following examples to create commonly used advanced filters, via the portal or API.

Don't collect specific event IDs

This filter instructs the connector not to collect EventID 256 or EventID 257 or EventID 260 with IPv6 addresses.

Using the Microsoft Sentinel portal:

  1. Create a filter with the EventOriginalType field, using the Equals operator, with the values 256, 257, and 260.

    Screenshot of filtering out event IDs for the Windows D N S over A M A connector.

  2. Create a filter with the EventOriginalType field defined above, and using the And operator, also including the DnsQueryTypeName field set to AAAA.

    Screenshot of filtering out event IDs and IPv6 addresses for the Windows D N S over A M A connector.

Using the API:

"Filters": [
    {
        "FilterName": "SampleFilter",
        "Rules": [
            {
                "Field": "EventOriginalType",
                "FieldValues": [
                    "256", "257", "260"                                                                              
                ]
            },
            {
                "Field": "DnsQueryTypeName",
                "FieldValues": [
                    "AAAA"                                        
                ]
            }
        ]
    },
    {
        "FilterName": "EventResultDetails",
        "Rules": [
            {
                "Field": "EventOriginalType",
                "FieldValues": [
                    "230"                                        
                ]
            },
            {
                "Field": "EventResultDetails",
                "FieldValues": [
                    "BADKEY","NOTZONE"                                        
                ]
            }
        ]
    }
]

Don't collect events with specific domains

This filter instructs the connector not to collect events from any subdomains of microsoft.com, google.com, amazon.com, or events from facebook.com or center.local.

Using the Microsoft Sentinel portal:

Set the DnsQuery field using the Equals operator, with the list *.microsoft.com,*.google.com,facebook.com,*.amazon.com,center.local.

Review these considerations for using wildcards.

Screenshot of filtering out domains for the Windows D N S over A M A connector.

To define different values in a single field, use the OR operator.

Using the API:

Review these considerations for using wildcards.

"Filters": [ 

    { 

        "FilterName": "SampleFilter", 

        "Rules": [ 

            { 

                "Field": "DnsQuery", 

                "FieldValues": [ 

                    "*.microsoft.com", "*.google.com", "facebook.com", "*.amazon.com","center.local"                                                                               

                ] 

            }, 

         } 

    } 

]

Normalization using ASIM

This connector is fully normalized using Advanced Security Information Model (ASIM) parsers. The connector streams events originated from the analytical logs into the normalized table named ASimDnsActivityLogs. This table acts as a translator, using one unified language, shared across all DNS connectors to come.

For a source-agnostic parser that unifies all DNS data and ensures that your analysis runs across all configured sources, use the ASIM DNS unifying parser _Im_Dns.

The ASIM unifying parser complements the native ASimDnsActivityLogs table. While the native table is ASIM compliant, the parser is needed to add capabilities, such as aliases, available only at query time, and to combine ASimDnsActivityLogs  with other DNS data sources.

The ASIM DNS schema represents the DNS protocol activity, as logged in the Windows DNS server in the analytical logs. The schema is governed by official parameter lists and RFCs that define fields and values.

See the list of Windows DNS server fields translated into the normalized field names.

Related content

In this article, you learned how to set up the Windows DNS events via AMA connector to upload data and filter your Windows DNS logs. To learn more about Microsoft Sentinel, see the following articles: