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cis-ubuntu1204-v110-7-2-6

DevOps & Security
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Enable Bad Error Message Protection

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_12.04_LTS_Server_Benchmark_v1.1.0/cis-ubuntu1204-v110-7-2-6/SKILL.md

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7.2.6 Enable Bad Error Message Protection (Scored)

Profile Applicability

  • Level 1

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

Using Command Line

Perform the following to determine if bogus messages will be ignored.

/sbin/sysctl net.ipv4.icmp_ignore_bogus_error_responses

Expected Result

net.ipv4.icmp_ignore_bogus_error_responses = 1

Remediation

Using Command Line

Set the net.ipv4.icmp_ignore_bogus_error_responses parameter to 1 in /etc/sysctl.conf:

net.ipv4.icmp_ignore_bogus_error_responses=1

Modify active kernel parameters to match:

/sbin/sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
/sbin/sysctl -w net.ipv4.route.flush=1

Default Value

Bogus error message protection is disabled by default.

References

  • CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

Profile

Level 1 - Scored