The Photon operating system must not respond to IPv4 Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.

Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.

At the command line, run the following command to verify ICMP echoes sent to a broadcast address are ignored:

# /sbin/sysctl net.ipv4.icmp_echo_ignore_broadcasts

Example result:

net.ipv4.icmp_echo_ignore_broadcasts = 1

If the "net.ipv4.icmp_echo_ignore_broadcasts" kernel parameter is not set to "1", this is a finding.

Navigate to and open:

/etc/sysctl.d/zz-stig-hardening.conf

Add or update the following line:

net.ipv4.icmp_echo_ignore_broadcasts = 1

At the command line, run the following command to load the new configuration:

# /sbin/sysctl --load /etc/sysctl.d/zz-stig-hardening.conf

Note: If the file zz-stig-hardening.conf does not exist, it must be created.