The Oracle Linux operating system must not respond to Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.
If "net.ipv4.icmp_echo_ignore_broadcasts" is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "1", this is a finding.
Check that the operating system implements the "icmp_echo_ignore_broadcasts" variable with the following command:
# /sbin/sysctl -a | grep net.ipv4.icmp_echo_ignore_broadcasts net.ipv4.icmp_echo_ignore_broadcasts = 1
If the returned line does not have a value of "1", this is a finding.
Fix
Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value):
net.ipv4.icmp_echo_ignore_broadcasts = 1
Issue the following command to make the changes take effect: