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3.1 Ensure That the Default Network Does Not Exist in a Project (Automated)​

Profile Applicability​

• Level 2

Description​

To prevent use of default network, a project should not have a default network.

Rationale​

The default network has a preconfigured network configuration and automatically generates the following insecure firewall rules:

  • default-allow-internal: Allows ingress connections for all protocols and ports among instances in the network.
  • default-allow-ssh: Allows ingress connections on TCP port 22(SSH) from any source to any instance in the network.
  • default-allow-rdp: Allows ingress connections on TCP port 3389(RDP) from any source to any instance in the network.
  • default-allow-icmp: Allows ingress ICMP traffic from any source to any instance in the network.

These automatically created firewall rules do not get audit logged and cannot be configured to enable firewall rule logging.

Furthermore, the default network is an auto mode network, which means that its subnets use the same predefined range of IP addresses, and as a result, it's not possible to use Cloud VPN or VPC Network Peering with the default network.

Based on organization security and networking requirements, the organization should create a new network and delete the default network.

Impact​

When an organization deletes the default network, it may need to migrate or service onto a new network.

Audit​

From Console:

  1. Go to the VPC networks page by visiting: https://console.cloud.google.com/networking/networks/list.

  2. Ensure that a network with the name default is not present.

From Command Line:

  1. Set the project name in the Google Cloud Shell:

gcloud config set project PROJECT_ID
  1. List the networks configured in that project:
gcloud compute networks list

It should not list default as one of the available networks in that project.

Remediation​

From Console:

  1. Go to the Virtual Private Cloud (VPC) networks page by visiting: https://console.cloud.google.com/networking/networks/list.

  2. Click the network named default.

  3. On the network detail page, click Edit.

  4. Click DELETE VPC NETWORK.

  5. If needed, create a new network to replace the default network.

From Command Line:

For each Google Cloud Platform project,

  1. Delete the default network:
gcloud compute networks delete default
  1. If needed, create a new network to replace it:
gcloud compute networks create network_name

Prevention:

You can prevent creation of the default network and its insecure default firewall rules by setting up an Organization Policy to Skip default network creation at https://console.cloud.google.com/iam-admin/orgpolicies/compute-skipDefaultNetworkCreation.

References​

https://cloud.google.com/compute/docs/networking#firewall_rules
https://cloud.google.com/compute/docs/reference/latest/networks/insert
https://cloud.google.com/compute/docs/reference/latest/networks/delete
https://cloud.google.com/vpc/docs/firewall-rules-logging
https://cloud.google.com/vpc/docs/vpc#default-network
https://cloud.google.com/sdk/gcloud/reference/compute/networks/delete

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