Detections
Analytics

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

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_locale.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.

See Also

https://workbench.cisecurity.org/benchmarks/13007

Item Details

Category: AUDIT AND ACCOUNTABILITY

References: 800-53|AU-3, 800-53|AU-3(1), 800-53|AU-7, 800-53|AU-12, CSCv7|5.5

Plugin: Unix

Control ID: b8c4d9ffb2e8a2b4e9de5918eefa250927365325682fa704d688706f7a811f7c