🛡️ Google GCE Network allows unrestricted DNS traffic🟢
- Contextual name: 🛡️ GCE Network allows unrestricted DNS traffic🟢
- ID:
/ce/ca/google/vpc/network-dns-access - Tags:
- Policy Type:
COMPLIANCE_POLICY - Policy Categories:
SECURITY
Logic
Description
Description
This policy identifies Google GCE Networks that have Firewall Rules allowing unrestricted incoming traffic (
0.0.0.0/0) from the internet to the DNS port (53) over TCP or UDP.In GCP, Firewall Rules are defined at the VPC Network level. Each rule either allows or denies traffic based on its configuration. These configurations specify the type of traffic (e.g., protocols and ports) and the source or destination (e.g., IP addresses, subnets, and instances).
Rationale
Exposing a VM’s DNS service to the public internet presents a significant security risk. Open DNS resolvers can be abused by attackers to launch DNS amplification and reflection attacks, a type of Distributed Denial-of-Service (DDoS) attack. By sending small, forged DNS queries to an open resolver, an attacker can force it to generate much larger responses directed at a target, potentially overwhelming the target network.
Access to DNS services should be restricted to trusted sources only, to prevent misuse of your infrastructure for such attacks.
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Remediation
Remediation
From Google Cloud Console
- Go to
VPC Network.- Go to the
Firewall Rules.- Click the
Firewall Ruleto be modified.- Click
Edit.- Modify
Source IP rangesto specificIP.- Click
Save.From Google Cloud CLI
Identify Firewall Rules Allowing Public Access
gcloud compute networks get-effective-firewalls default \
--format="table(NAME, DIRECTION, IP_RANGES)" \
--filter="IP_RANGES:0.0.0.0/0 AND DIRECTION:INGRESS"Restrict the Source Range
Once you have identified the firewall rules, update each one to restrict access to trusted CIDR ranges:
gcloud compute firewall-rules update {{firewall-rule-name}} \
--source-ranges={{cidr-range1}},{{cidr-range2}}