Block broadcast and multicast packets with IPtables match extension 'pkt-type'

With the IPtables match extension for packet types it is very easy to filter out unwanted broadcast and multicast packets from the logs.

iptables -A INPUT -m pkttype --pkt-type broadcast -j DROP
iptables -A INPUT -m pkttype --pkt-type multicast -j DROP

man iptables(8)
Match extension 'pkttype'
This module matches the link-layer packet type.
--pkt-type [unicast|broadcast|multicast]