cis-ubuntu1604-v200-4-1-5

DevOps & Security

Ensure events that modify the system's network environment are collected

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_16.04_LTS_Benchmark_v2.0.0/cis-ubuntu1604-v200-4-1-5/SKILL.md

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 4.1.5

Profile

Level: 2 - Server
Level: 2 - Workstation
Assessment Status: Automated

Description

Record changes to network environment files or system calls. The below parameters monitor the sethostname (set the systems host name) or setdomainname (set the systems domainname) system calls, and write an audit event on system call exit. The other parameters monitor the /etc/issue and /etc/issue.net files (messages displayed pre-login), /etc/hosts (file containing host names and associated IP addresses) and /etc/network (directory containing network interface scripts and configurations) files.

Note: Reloading the auditd config to set active settings requires the auditd service to be restarted, and may require a system reboot.

Rationale

Monitoring sethostname and setdomainname will identify potential unauthorized changes to host and domainname of a system. The changing of these names could potentially break security parameters that are set based on those names. The /etc/hosts file is monitored for changes in the file that can indicate an unauthorized intruder is trying to change machine associations with IP addresses and trick users and processes into connecting to unintended machines. Monitoring /etc/issue and /etc/issue.net is important, as intruders could put disinformation into those files and trick users into providing information to the intruder. Monitoring /etc/network is important as it can show if network interfaces or scripts are being modified in a way that can lead to the machine becoming unavailable or compromised. All audit records will be tagged with the identifier "system-locale."

Impact

None.

Audit Procedure

Command Line

On a 32 bit system:

Run the following command to verify the rules are contained in a .rules file in the /etc/audit/rules.d/ directory:

grep system-locale /etc/audit/rules.d/*.rules

Verify the output matches:

-a always,exit -F arch=b32 -S sethostname -S setdomainname -k system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

Run the following command to verify that rules are in the running auditd config:

auditctl -l | grep system-locale

Verify the output matches:

-a always,exit -F arch=b32 -S sethostname,setdomainname -F key=system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

On a 64 bit system:

Run the following command to verify the rules are contained in a .rules file in the /etc/audit/rules.d/ directory:

grep system-locale /etc/audit/rules.d/*.rules

Verify the output matches:

-a always,exit -F arch=b64 -S sethostname -S setdomainname -k system-locale
-a always,exit -F arch=b32 -S sethostname -S setdomainname -k system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

Run the following command to verify that rules are in the running auditd config:

auditctl -l | grep system-locale

Verify the output matches:

-a always,exit -F arch=b64 -S sethostname,setdomainname -F key=system-locale
-a always,exit -F arch=b32 -S sethostname,setdomainname -F key=system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

Expected Result

Output should match the rules listed above for the appropriate architecture.

Remediation

Command Line

For 32 bit systems: Edit or create a file in the /etc/audit/rules.d/ directory ending in .rules.

Example: vi /etc/audit/rules.d/50-system-locale.rules

Add the following lines:

-a always,exit -F arch=b32 -S sethostname -S setdomainname -k system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

For 64 bit systems: Edit or create a file in the /etc/audit/rules.d/ directory ending in .rules.

Example: vi /etc/audit/rules.d/50-system-locale.rules

Add the following lines:

-a always,exit -F arch=b64 -S sethostname -S setdomainname -k system-locale
-a always,exit -F arch=b32 -S sethostname -S setdomainname -k system-locale
-w /etc/issue -p wa -k system-locale
-w /etc/issue.net -p wa -k system-locale
-w /etc/hosts -p wa -k system-locale
-w /etc/network -p wa -k system-locale

Default Value

By default, no audit rules are configured for network environment changes.

References

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Section 4.1.5

CIS Controls

Controls Version	Control
v7	5.5 Implement Automated Configuration Monitoring Systems - Utilize a Security Content Automation Protocol (SCAP) compliant configuration monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur.