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Decrypt domain traffic with a Windows domain controller

The ExtraHop system can be configured to retrieve and store domain keys from a domain controller. When the system observes encrypted traffic that matches the stored keys, all of the Kerberos-encrypted traffic in the domain is decrypted for supported protocols. The system only synchronizes Kerberos and NTLM decryption keys and does not modify any other properties in the domain.

A domain controller like Active Directory is a frequent target for attackers because a successful attack campaign yields high-value targets. Critical attacks can be obscured by Kerberos or NTLM decryption, such as Golden Ticket, PrintNightmare, and Bloodhound. Decrypting this type of traffic can provide deeper insight for security detections.

You can enable decryption on an individual sensor or through an integration on RevealX 360.

The following requirements must be met for decryption:

  • You must have an Active Directory domain controller (DC) that is not configured as a Read-only Domain Controller (RODC).
  • Only Windows Server 2016, Windows Server 2019, and Windows Server 2022 are supported.
  • Only one domain controller can be configured on a sensor, which means you can decrypt the traffic from one domain per sensor.
  • The ExtraHop system synchronizes keys for up to 50,000 accounts in a configured domain. If your DC has more than 50,000 accounts, some traffic will not be decrypted.
  • The ExtraHop system must observe the network traffic between the DC and connected clients and servers.
  • The ExtraHop system must be able to access the domain controller over the following ports: TCP 88 (Kerberos), TCP 445 (SMB), TCP 135 (RPC), and TCP ports 49152-65535 (RPC dynamic range).
Warning:If you enable these settings, the ExtraHop system is granted access to all of the account keys in the Windows domain. The ExtraHop system should be deployed at the same security level as the domain controller. Here are some best practices to consider:
  • Strictly limit end-user access to sensors that are configured with access to the domain controller. Ideally, only permit end-user access to a connected console.
  • Configure sensors with an identity provider that has strong authentication features such as two-factor or multi-factor authentication.
  • Restrict inbound and outbound traffic to and from the sensor to only what is needed.
  • In Active Directory, limit the Logon Workstations for the account to only communicate with the domain controller that the ExtraHop system is configured with.

Connect a domain controller to a sensor

Before you begin

You must have a user account with setup or system and access administration privileges on the sensor.
  1. Log in to the Administration settings on the ExtraHop system through https://<extrahop-hostname-or-IP-address>/admin.
  2. In the System Configuration section, click Capture.
  3. Click Domain Controller.
  4. Select the Enable connection to the domain controller checkbox.
  5. Complete the following fields:

    Hostname: The fully qualified domain name of the domain controller.

    Computer Name (sAMAccountName): The name of the domain controller.

    Realm Name: The name of the Kerberos realm where the domain controller has authority.

    User Name: The name of a user who is a member of the built-in Administrators group for the domain (not to be confused with the Domain Admins group). To prevent possible connection errors, specify a user account created after the domain controller was established.

    Password: The password of the privileged user.

  6. Click Test Connection to confirm that the sensor can communicate with the domain controller.
  7. Click Save.

Connect a domain controller to a RevealX 360 sensor

Before you begin

Your user account must have privileges on RevealX 360 for System and Access Administration.
  1. Log into RevealX 360.
  2. Click the System Settings icon and then click Integrations.
  3. Click the Microsoft Protocol Decryption tile.
  4. Complete the following fields to specify credentials for the Microsoft Active Directory domain controller you want to connect to a RevealX 360 sensor:

    Hostname: The fully qualified domain name of the domain controller.

    Computer Name (sAMAccountName): The name of the domain controller.

    Realm Name: The name of the Kerberos realm where the domain controller has authority.

    User Name: The name of a user who is a member of the built-in Administrators group for the domain (not to be confused with the Domain Admins group). To prevent possible connection errors, specify a user account created after the domain controller was established.

    Password: The password of the privileged user.

  5. From the drop-down list, select the RevealX 360 sensor the domain controller will connect to. Only one domain controller can be connected to a RevealX 360 sensor.
  6. Click Test Connection to confirm that the sensor can communicate with the domain controller.
  7. Click Save.

Validate the configuration settings

To validate that the ExtraHop system is able to decrypt traffic with the configured domain controller, go to the built-in Microsoft Protocol Decryption dashboard to identify successful decryption attempts.

Each chart in the Microsoft Protocol Decryption dashboard contains visualizations of Kerberos decryption data that have been generated over the selected time interval, organized by region.

The Microsoft Protocol Decryption dashboard is a built-in, system dashboard that you cannot edit, delete, or add to a shared collection. However, you can copy a chart from the Microsoft Protocol Decryption dashboard and add it to a custom dashboard, or you can make a copy of the dashboard and edit it to monitor metrics that are relevant to you.

Note:The Microsoft Protocol Decryption dashboard can only be viewed on a console.

The following information summarizes each region and its charts.

Kerberos Decryption Attempts
Observe the number of Kerberos decryption attempts in your environment in the following charts:

Successful Kerberos Decryption Attempts: Total number of successful Kerberos decryption attempts and when they occurred.

Total Successful Attempts: Total number of successful Kerberos decryption attempts.

Unsuccessful Kerberos Decryption Attempts: Total number of unsuccessful Kerberos decryption attempts and when they occurred, listed by the reason the attempt failed.

Total Unsuccessful Attempts: Total number of unsuccessful Kerberos decryption attempts, listed by the reason the attempt failed.

Unsuccessful Kerberos Decryption Details
Observe details about unsuccessful Kerberos decryption attempts in the following charts:

Unrecognized Server Principal Names: Total number of Kerberos decryption attempts that failed due to an unrecognized server principal name (SPN), listed by the SPN. Displayed as a bar chart and a list chart.

Invalid Kerberos Keys: Total number of Kerberos decryption attempts that failed due to an invalid Kerberos key, listed by the SPN that made the attempt. Displayed as a bar chart and a list chart.

Kerberos Decryption Errors : Total number of Kerberos decryption attempts that failed due to an error, listed by the SPN that made the attempt. Displayed as a bar chart and a list chart.

Server Principal Name Details
Observe the top SPN that made Kerberos decryption attempts in the following charts:

Top Server Principal Names: Top 50 SPNs that made Kerberos decryption attempts and the following details:

  • The number of successful decryption attempts.
  • The number of unsuccessful attempts due to an invalid Kerberos key.
  • The number of unsuccessful attempts due to an error.
  • The number of unsuccessful attempts due an unrecognized SPN.

Additional system health metrics

The ExtraHop system provides metrics that you can add to a dashboard to monitor DC-assisted decryption health and functionality.

To view a list of available metrics, click the System Settings icon and then click Metric Catalog. Type DC-Assisted in the filter field to display all available DC-assisted decryption metrics.



Last modified 2024-12-06