cyberstrikeus 3.2.6 Ensure bogus ICMP responses are ignored (Automated)
Description
Setting icmp_ignore_bogus_error_responses to 1 prevents the kernel from logging bogus responses (RFC-1122 non-compliant) from broadcast reframes, keeping file systems from filling up with useless log messages.
Rationale
Some routers (and some attackers) will send responses that violate RFC-1122 and attempt to fill up a log file system with many useless error messages.
Audit Procedure
Run the following commands and verify output matches:
# sysctl net.ipv4.icmp_ignore_bogus_error_responses
net.ipv4.icmp_ignore_bogus_error_responses = 1
# grep "net.ipv4.icmp_ignore_bogus_error_responses" /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.icmp_ignore_bogus_error_responses = 1
Expected Result
The sysctl command should return a value of 1 and the grep command should confirm the setting is persisted in the sysctl configuration files.
Remediation
Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.icmp_ignore_bogus_error_responses = 1
Run the following commands to set the active kernel parameters:
# sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
# sysctl -w net.ipv4.route.flush=1
/etc is stateless on Container-Optimized OS. Therefore, /etc cannot be used to make these changes persistent across reboots. The steps mentioned above needs to be performed after every boot.
CIS Controls
| Controls Version | Control | IG 1 | IG 2 | IG 3 |
|---|---|---|---|---|
| v8 | 12.2 Establish and Maintain a Secure Network Architecture - Establish and maintain a secure network architecture. A secure network architecture must address segmentation, least privilege, and availability, at a minimum. | X | X | |
| v7 | 5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software. | X | X | X |
Profile
- Level 1 - Server