Attack Chain

1. The attacker gains unauthorized access to a GCP account with sufficient privileges to modify VPC configurations. This could be achieved through compromised credentials, privilege escalation, or exploiting misconfigured IAM roles.
2. The attacker enumerates existing VPC routes to identify potential targets for disruption, using tools like gcloud compute routes list.
3. The attacker selects a critical VPC route that is essential for network communication between key services or network segments.
4. The attacker deletes the selected VPC route using gcloud compute routes delete [ROUTE_NAME], causing a disruption in network traffic flow.
5. The successful deletion of the route is logged in GCP audit logs.
6. Network services relying on the deleted route experience connectivity issues, leading to service degradation or failure.
7. The attacker may repeat this process with other critical routes to further isolate network segments or prevent detection.

Impact

Successful deletion of VPC routes can lead to significant disruptions in network connectivity and service availability. Victims may experience degraded performance, application failures, or complete outages, depending on the criticality of the affected routes. The deletion of VPC routes can affect any organization utilizing GCP, especially those reliant on stable and predictable network traffic patterns. The risk score associated with this activity is 47.

Recommendation

• Deploy the provided Sigma rule to your SIEM to detect VPC route deletion events in GCP audit logs (logsource: service: gcp and category: audit).
• Review and harden IAM permissions to restrict access to VPC route management functions to authorized personnel only.
• Implement automated monitoring and alerting for any changes to VPC route configurations.
• Investigate any alerts generated by the Sigma rule by reviewing the associated audit logs and identifying the user or service account responsible for the route deletion.
• Establish a process for quickly restoring deleted VPC routes from backups or configuration management tools.
• Implement the recommendations in the provided investigation guide to analyze the context and impact of route deletion events.

Attack Chain

1. An attacker gains unauthorized access to a GCP account with sufficient privileges. This could be via compromised credentials, or a misconfigured IAM role.
2. The attacker enumerates available VPC networks within the GCP project to identify a target for disruption.
3. The attacker executes a command or API call to initiate the deletion of the chosen VPC network. This could be done via the gcloud CLI or the GCP console.
4. GCP validates the attacker's permissions and initiates the VPC network deletion process.
5. The VPC network and all associated resources (subnets, routes, firewall rules) are removed from the GCP environment.
6. Applications and services relying on the deleted VPC network experience connectivity issues and service disruptions.
7. The attacker monitors the impact of the VPC network deletion to ensure the desired disruption has occurred.
8. The attacker attempts to cover their tracks by deleting audit logs or other evidence of their actions.

Impact

Successful deletion of a VPC network can severely disrupt business operations. Applications and services relying on the deleted network will experience connectivity issues and may become unavailable. This can lead to data loss, financial losses, and reputational damage. The severity depends on the criticality of the affected applications and the speed of recovery. While specific numbers of victims are not provided, the impact can range from isolated application failures to widespread outage affecting entire organizations depending on their GCP infrastructure.

Recommendation

• Deploy the GCP VPC Network Deletion Sigma rule to your SIEM to detect unauthorized VPC network deletions. Ensure the log source is configured to ingest GCP audit logs.
• Review and harden IAM policies to enforce the principle of least privilege for VPC network management.
• Monitor GCP audit logs for unusual activity related to VPC network configurations, focusing on the event.action:v*.compute.networks.delete event.
• Implement multi-factor authentication (MFA) for all GCP accounts with administrative privileges.
• Create exceptions in the GCP VPC Network Deletion rule for authorized and expected VPC network deletions.

Attack Chain

1. An attacker gains initial access to an AWS account, possibly through compromised credentials or by exploiting a misconfigured IAM role.
2. The attacker leverages the AWS CLI or Management Console to create a new Network ACL.
3. The attacker configures the Network ACL to allow inbound and outbound traffic on all ports (0-65535), effectively bypassing network segmentation controls.
4. The attacker associates the newly created, overly permissive Network ACL with one or more subnets within a Virtual Private Cloud (VPC).
5. The attacker probes the exposed resources within the subnet to identify potential targets.
6. The attacker exploits vulnerabilities in exposed services, such as databases or web applications, due to the lack of network filtering.
7. The attacker gains unauthorized access to sensitive data or systems within the VPC.

Impact

Creating an AWS Network ACL with all ports open significantly increases the risk of unauthorized access to resources within a VPC. This misconfiguration can lead to data breaches, service disruptions, and other security incidents. The impact depends on the sensitivity of the data and systems exposed, but could potentially affect thousands of customers if it involves a multi-tenant environment. It is critical to monitor for and remediate overly permissive Network ACLs to maintain a strong security posture.