There have been several broadcast amplification attacks against IPv4 network infrastructures. The most famous was the smurf attack where the attacker sent out the packet with following content:

There were two problems that allowed the smurf attack to work:

1. Ingress filtering was not implemented which allowed spoofing the source address field of the attack packet.

2. The host operating systems answered to a message destined to a broadcast address. Such a problem cannot be foreseen in IPv6 environment for various reasons:

There is no broadcast address in IPv6 environment

This would stop any type of amplification/smurf attacks that send ICMP packets to the broadcast address. However global multicast addresses for special groups of devices, e.g. linklocal addresses, site-local addresses, all site-local routers, etc. are available to reach groups of devices.

The IPv6 specification does not allow answering to multicast destinations

IPv6 specifications forbid the generation of ICMPv6 packets in response to messages to global multicast addresses except in two case as described in RFC 1885 [RFC1885]:

1. The Packet Too Big Message - to allow Path MTU discovery to work for IPv6 multicast
2. The Parameter Problem Message, Code 2 - reporting an unrecognized IPv6 option that has the Option Type highest-order two its set to 10.