🛡️ Google GCE Network allows unrestricted NetBIOS traffic🟢
- Contextual name: 🛡️ GCE Network has Firewall Rules which allow unrestricted NetBIOS access from the Internet🟢
- ID:
/ce/ca/google/vpc/network-netbios-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 NetBIOS ports: (TCP/UDP)137,138, and139.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
NetBIOS is a legacy protocol used for name resolution and file/printer sharing in older Windows environments. It is not designed to be exposed to the public internet and has a long history of security vulnerabilities. Public exposure of these ports can lead to information disclosure, denial-of-service attacks, and exploitation by worms or malware that target NetBIOS services. There is almost no legitimate reason to allow unrestricted public access to these ports.
Impact
All NetBIOS connections from outside of the network to the concerned VPC(s) can be blocked. If there is a legitimate operational need for remote access, specific trusted source IP addresses should be explicitly defined in firewall rules to whitelist access only to the required NetBIOS ports.
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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}}