TOSS must not respond to Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.
An XCCDF Rule
Description
Responding to broadcast ICMP echoes facilitates network mapping and provides a vector for amplification attacks. There are notable differences between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). IPv6 does not implement the same method of broadcast as IPv4. Instead, IPv6 uses multicast addressing to the all-hosts multicast group. Refer to RFC4294 for an explanation of "IPv6 Node Requirements", which resulted in this difference between IPv4 and IPv6.
- ID
- SV-253128r991589_rule
- Version
- TOSS-04-040870
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Configure TOSS to not respond to IPv4 ICMP echoes sent to a broadcast address with the following command:
$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
If "1" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":
net.ipv4.icmp_echo_ignore_broadcasts=1