The NSX Tier-0 Gateway router must be configured to have Internet Control Message Protocol (ICMP) mask replies disabled on all external interfaces.

An XCCDF Rule

Description

The ICMP supports IP traffic by relaying information about paths, routes, and network conditions. Routers automatically send ICMP messages under a wide variety of conditions. Mask Reply ICMP messages are commonly used by attackers for network mapping and diagnosis.

ID: SV-265442r999916_rule
Version: NT0R-4X-000065
Severity: Medium
References: CCI-002385
Updated: about 2 months ago

Remediation Templates

To configure a shared rule to drop ICMP unreachable messages, do the following:

From the NSX Manager web interface, go to Security >> Policy Management >> Gateway Firewall >> All Shared Rules.

Click "Add Rule" (add a policy first if needed). Under "Services", select the custom service that identifies ICMP mask replies, and then click "Apply".
Enable logging, under the "Applied To" field select the target Tier-0 gateways' external interfaces, and then select "Publish" to enforce the new rule.

Note: A rule can also be created under Gateway Specific Rules to meet this requirement.

Note: A pre-created service for ICMP mask replies does not exist by default and may need created.

The NSX Tier-0 Gateway router must be configured to have Internet Control Message Protocol (ICMP) mask replies disabled on all external interfaces.

Description

Remediation Templates

A Manual Procedure