Description

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

Rationale

Monitoring create or update firewall rule events gives insight to network access changes and may reduce the time it takes to detect suspicious activity.

Impact

Enabling logging may result in your project being charged for the additional logs usage.

Remediation

From the 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 a prescribed alert policy

1. Go to https://console.cloud.google.com/logs/metrics. Under the User-defined Metrics section, identify the newly created metric.
2. Click the kebab icon in the rightmost column for the new metric and select Create alert from Metric.
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 the command line

Create a prescribed log metric

Use the command: gcloud logging metrics create Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/beta/logging/metrics/create

Create a prescribed alert policy

Use the command: gcloud alpha monitoring policies create Reference for command usage: https://cloud.google.com/sdk/gcloud/reference/alpha/monitoring/policies/create

References

1. https://cloud.google.com/logging/docs/logs-based-metrics/
2. https://cloud.google.com/monitoring/custom-metrics/
3. https://cloud.google.com/monitoring/alerts/
4. https://cloud.google.com/logging/docs/reference/tools/gcloud-logging
5. https://cloud.google.com/vpc/docs/firewalls