Ensure That the Log Metric Filter and Alerts Exist for VPC Network Firewall Rule Changes

Description:

It is recommended that a metric filter and alarm be established for Virtual Private Cloud (VPC) Network Firewall rule changes.

Rationale:

Monitoring for Create or Update Firewall rule events gives insight to network access changes and may reduce the time it takes to detect suspicious activity.

Enabling of logging may result in your project being charged for the additional logs usage. These charges could be significant depending on the size of the organization.

From Google Cloud Console

Create the prescribed log metric:

1. Go to 'Logging/Logs-based Metrics' by visiting https://console.cloud.google.com/logs/metrics and click "CREATE METRIC".

2. Click the down arrow symbol on the 'Filter Bar' at the rightmost corner and select 'Convert to Advanced Filter'.

3. Clear any text and add:

resource.type="gce_firewall_rule"
AND (protoPayload.methodName:"compute.firewalls.patch"
OR protoPayload.methodName:"compute.firewalls.insert"
OR protoPayload.methodName:"compute.firewalls.delete")

4. Click 'Submit Filter'. Display logs appear based on the filter text entered by the user.

5. In the 'Metric Editor' menu on the right, fill out the name field. Set 'Units' to '1' (default) and 'Type' to 'Counter'. This ensures that the log metric counts the number of log entries matching the advanced logs query.

6. Click 'Create Metric'.

Create the prescribed Alert Policy:

1. Identify the newly created metric under the section 'User-defined Metrics' at https://console.cloud.google.com/logs/metrics.

2. Click the 3-dot icon in the rightmost column for the new metric and select 'Create alert from Metric'. A new page displays.

3. Fill out the alert policy configuration and click 'Save'. Choose the alerting threshold and configuration that makes sense for the user's organization. For example, a threshold of zero(0) for the most recent value ensures that a notification is triggered for every owner change in the project:

Set 'Aggregator' to 'Count'

Set 'Configuration':

• Condition: above

• Threshold: 0

• For: most recent value

4. Configure the desired notifications channels in the section 'Notifications'.

5. Name the policy and click 'Save'.

From Google Cloud CLI

Create the prescribed Log Metric

• Use the command: gcloud logging metrics create

Create the prescribed alert policy:

• Use the command: gcloud alpha monitoring policies create