Use the Conformity Knowledge Base AI to help improve your Cloud Posture

Enable Virtual Machine IP Forwarding Monitoring

Trend Cloud One™ – Conformity is a continuous assurance tool that provides peace of mind for your cloud infrastructure, delivering over 1000 automated best practice checks.

Risk Level: Medium (should be achieved)
Rule ID: SecurityCenter-023

Ensure that the IP forwarding feature enabled for your Microsoft Azure virtual machines (VMs) is being monitored by the Azure Security Center service for security and compliance purposes.

This rule resolution is part of the Conformity Security & Compliance tool for Azure.

Security

Enabling IP forwarding on a virtual machine's network interface (NIC) allows the machine to act as a router and receive traffic addressed to other destinations. IP forwarding is rarely required (for example, when using the virtual machine as a network virtual appliance), therefore the feature should be monitored in order to be audited by your network security team.


Audit

To determine if the IP forwarding feature for virtual machines is continuously monitored using Microsoft Defender for Cloud, perform the following actions:

Using Azure Portal

01 Sign in to the Microsoft Azure Portal.

02 Navigate to Microsoft Defender for Cloud blade at https://portal.azure.com/#blade/Microsoft_Azure_Security/SecurityMenuBlade/0.

03 In the main navigation panel, under Management, choose Environment settings.

04 Click on the name (link) of the Azure subscription that you want to examine.

05 In the navigation panel, under Policy settings, choose Security policy.

06 In the Default initiative section, click on the name of the default initiative enabled for the selected subscription (i.e. ASC Default (subscription: <subscription-id>)).

07 Choose the Parameters tab, uncheck Only show parameters that need input or review, and search for the following parameter: IP Forwarding on your virtual machine should be disabled. If the IP Forwarding on your virtual machine should be disabled parameter is set to Disabled, the monitoring of IP forwarding on Azure virtual machines (VMs) is not enabled in the selected subscription.

08 Repeat steps no. 4 – 7 for each Microsoft Azure subscription created within your Azure account.

Using Azure CLI

01 Run account get-access-token command (Windows/macOS/Linux) using custom query filters to determine if the virtual machine IP forwarding monitoring is enabled within the current Azure subscription by checking the disableIPForwardingMonitoringEffect configuration parameter value:

az account get-access-token
  --query "{subscription:subscription,accessToken:accessToken}"
  --out tsv | xargs -L1 bash -c 'curl -X GET -H "Authorization: Bearer $1" -H "Content-Type: application/json" https://management.azure.com/subscriptions/$0/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn?api-version=2018-05-01' | jq 'select(.name=="SecurityCenterBuiltIn")'|jq '.properties.parameters.disableIPForwardingMonitoringEffect.value'

02 The command output should return the requested parameter value:

"Disabled"

If the account get-access-token command output returns "Disabled", as shown in the output example above, the monitoring of IP forwarding on Azure virtual machines (VMs) is not enabled within the current subscription.

03 Repeat steps no. 1 and 2 for each Microsoft Azure subscription available in your Azure cloud account.

Remediation / Resolution

To enable virtual machine IP forwarding monitoring using Microsoft Defender for Cloud, perform the following actions:

Using Azure Portal

01 Sign in to the Microsoft Azure Portal.

02 Navigate to Microsoft Defender for Cloud blade at https://portal.azure.com/#blade/Microsoft_Azure_Security/SecurityMenuBlade/0.

03 In the main navigation panel, under Management, choose Environment settings.

04 Click on the name (link) of the Azure subscription that you want to access.

05 In the navigation panel, under Policy settings, choose Security policy.

06 In the Default initiative section, click on the name of the default initiative enabled for the selected subscription (i.e. ASC Default (subscription: <subscription-id>)).

07 Choose the Parameters tab and uncheck the Only show parameters that need input or review checkbox to list all the initiative parameters.

08 Select AuditIfNotExists from the IP Forwarding on your virtual machine should be disabled parameter dropdown list to enable the monitoring of IP forwarding on your Azure virtual machines (VMs).

09 Select Review + save to review the configuration changes, then choose Save to apply the new changes. If the operation is successful, the following confirmation message should be displayed: "Updating policy assignment succeeded".

10 Repeat steps no. 4 – 9 for each Microsoft Azure subscription available within your Azure account.

Using Azure CLI

01 Define the configuration parameters for the account get-access-token command, where the disableIPForwardingMonitoringEffect parameter is enabled to turn on the system monitoring feature. Save the configuration document to a JSON file named enable-ip-forwarding-monitoring.json and replace the highlighted details, i.e. <azure-subscription-id> and <policy-definition-id>, with your own Azure account subscription details:

{
  "properties":{
     "displayName":"ASC Default (subscription: <azure-subscription-id>)",
     "policyDefinitionId":"/providers/Microsoft.Authorization/policySetDefinitions/<policy-definition-id>",
     "scope":"/subscriptions/<azure-subscription-id>",
     "parameters":{
        "disableIPForwardingMonitoringEffect":{
           "value":"AuditIfNotExists"
        }
     }
  },
  "id":"/subscriptions/<azure-subscription-id>/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn",
  "type":"Microsoft.Authorization/policyAssignments",
  "name":"SecurityCenterBuiltIn",
  "location":"eastus"
}

02 Run account get-access-token command (Windows/macOS/Linux) using the configuration document defined at the previous step (i.e. enable-ip-forwarding-monitoring.json file), to enable the monitoring of IP forwarding feature on your Azure virtual machines (VMs):

az account get-access-token
  --query "{subscription:subscription,accessToken:accessToken}"
  --out tsv | xargs -L1 bash -c 'curl -X PUT -H "Authorization: Bearer $1" -H "Content-Type: application/json" https://management.azure.com/subscriptions/$0/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn?api-version=2018-05-01 -d@"enable-ip-forwarding-monitoring.json"'

03 The command output should return information about the modified configuration parameter:

{
  "sku": {
    "name": "A0",
    "tier": "Free"
  },
  "properties": {
    "displayName": "ASC Default (subscription: abcdabcd-1234-1234-1234-abcdabcdabcd)",
    "policyDefinitionId": "/providers/Microsoft.Authorization/policySetDefinitions/1234abcd-1234-1234-1234-abcd1234abcd",
    "scope": "/subscriptions/abcdabcd-1234-1234-1234-abcdabcdabcd",
    "parameters": {
      "disableIPForwardingMonitoringEffect": {
        "value": "AuditIfNotExists"
      }
    },
    "metadata": {
      "createdBy": "abcdabcd-1234-1234-1234-abcdabcdabcd",
      "createdOn": "2019-05-17T15:38:40.3473931Z",
      "updatedBy": "1234abcd-1234-1234-1234-abcd1234abcd",
      "updatedOn": "2022-02-01T21:22:40.7422203Z"
    }
  },
  "id": "/subscriptions/abcdabcd-1234-1234-1234-abcdabcdabcd/providers/Microsoft.Authorization/policyAssignments/SecurityCenterBuiltIn",
  "type": "Microsoft.Authorization/policyAssignments",
  "name": "SecurityCenterBuiltIn",
  "location": "eastus"
}

04 Repeat steps no. 1 – 3 for each Microsoft Azure subscription available in your Azure cloud account.

References

Publication date Mar 27, 2020