If you have a firewall and not just a router, you can actually start blocking IP Ranges of countries that you don't need to allow inbound to your network - I block a large list of them, and it cuts down on a LOT of that type of thing, it also stops them from being able to access public services I offer to clients. Being from the USA, and not providing services to many foreign countries, here's the list I'm blocking:
12.144.182.0/24 12.45.203.0/24 12.98.139.0/24 155.48.106.0/24 168.126.0.0/16 172.184.111.203 193.251.0.0/16 193.252.0.0/16 193.253.0.0/16 195.174.0.0/16 195.175.16.0/20 195.58.124.0/24 200.30.203.0/24 202.88.186.0/24 203.152.22.0/24 205.251.79.0/24 210.173.37.0/24 210.201.153.0/24 210.71.115.0/24 211.54.40.0/25 212.150.124.0/24 212.18.57.0/24 212.202.178.0/24 212.27.32.0-212.27.63.255 212.64.192.0-212.64.203.255 212.64.223.160/29 212.64.223.168/29 212.9.7.0/24 213.13.26.0/24 213.144.176.0/24 213.190.213.0/24 213.228.7.0/24 213.228.8.0/24 216.184.97.0/24 216.76.35.0/24 217.118.224.0/24 217.118.225.0/24 217.118.239.0/24 217.160.110.0/24 218.164.28.0/24 218.252.74.0/24 218.67.128.0-218.69.255.255 218.69.108.0/24 218.69.148.0/24 218.76.98.0/24 219.212.4.0/24