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4.1.3.5 Ensure events that modify the system's network environment are collected - /etc/hosts

Warning! Audit Deprecated

This audit has been deprecated and will be removed in a future update.

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Information

Record changes to network environment files or system calls. The below parameters monitors the following system calls, and write an audit event on system call exit:

sethostname - set the systems host name

setdomainname - set the systems domain name

The files being monitored are:

/etc/issue and /etc/issue.net - messages displayed pre-login

/etc/hosts - file containing host names and associated IP addresses

/etc/networks - symbolic names for networks

/etc/network/ - directory containing network interface scripts and configurations files

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 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 should have a relevant tag associated with them.

Solution

Create audit rules


Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment.

64 Bit systems


Example:

# printf '
-a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale
-a always,exit -F arch=b32 -S sethostname,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/networks -p wa -k system-locale
-w /etc/network/ -p wa -k system-locale
' >> /etc/audit/rules.d/50-system_local.rules

Load audit rules


Merge and load the rules into active configuration:

# augenrules --load

Check if reboot is required.

# if [[ $(auditctl -s | grep 'enabled') =~ '2' ]]; then printf 'Reboot required to load rules
'; fi

32 Bit systems


Follow the same procedures as for 64 bit systems and ignore any entries with b64.

Additional Information:

Potential reboot required

If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration.

System call structure

For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page.

See Also

https://workbench.cisecurity.org/files/4068

Item Details

References: CSCv7|5.5

Plugin: Unix

Control ID: d11b8e4f0a02ea4cbfe2df2cc924c6efda8da3f86f1981afa812e32f157de211