The system must not respond to Internet Control Message Protocol v4 (ICMPv4) echoes sent to a broadcast address.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-001551

SV-64459r1_rule The system must not respond to Internet Control Message Protocol v4 (ICMPv4) echoes sent to a broadcast address.

Vulnerability discussion

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

Check content

Verify the system does not respond to ICMP ECHO_REQUESTs set to broadcast addresses. Procedure: # cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts If the result is not 1, this is a finding.

Fix text

Configure the system to not respond to ICMP ECHO_REQUESTs sent to broadcast addresses. Edit /etc/sysctl.conf and add a setting for "net.ipv4.icmp_echo_ignore_broadcasts=1" and reload the sysctls. Procedure: # echo "net.ipv4.icmp_echo_ignore_broadcasts=1" >> /etc/sysctl.conf # sysctl -p

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