Ubuntu OS audit event multiplexor must be configured to off-load audit logs onto a different system from the system being audited.

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

The auditd service does not include the ability to send audit records to a centralized server for management directly. However, it can use a plug-in for audit event multiplexor to pass audit records to a remote server.

Verify the audit event multiplexor is configured to off-load audit records to a different system from the system being audited.

Check if the "audispd-plugins" package is installed:

     $ dpkg -l | grep audispd-plugins 
     ii     audispd-plugins     1:3.0.7-1build1     amd64     Plugins for the audit event dispatcher 

If the "audispd-plugins" package is not installed, this is a finding.

Check that the records are being off-loaded to a remote server by using the following command:

     $ sudo grep -i active /etc/audit/plugins.d/au-remote.conf 
     active = yes  

If "active" is not set to "yes", or the line is commented out, or is missing, this is a finding.

Check that audisp-remote plugin is configured to send audit logs to a different system:

     $ sudo grep -i remote_server /etc/audit/audisp-remote.conf 
     remote_server = 240.9.19.81 

If the "remote_server" parameter is not set, is set with a local IP address, or is set with an invalid IP address, this is a finding.

Configure the audit event multiplexor to off-load audit records to a different system from the system being audited.

Install the "audisp-plugins" package by using the following command:

     $ sudo apt-get install audispd-plugins 

Set the audisp-remote plugin as active by editing the "/etc/audit/plugins.d/au-remote.conf" file:

     $ sudo sed -i -E 's/active\s*=\s*no/active = yes/' /etc/audit/plugins.d/au-remote.conf 

Set the IP address of the remote system by editing the "/etc/audit/audisp-remote.conf" file:

     $ sudo sed -i -E 's/(remote_server\s*=).*/\1 <remote_server_ip_address>/' /etc/audit/audisp-remote.conf 

Restart the "auditd.service" for the changes to take effect:

     $ sudo systemctl restart auditd.service