This article is concerning distributed reflection denial of service (DRDoS) attacks. These DRDoSattacks are more frequent and large scale, and are one of the biggest threats on the Internet. This paperdiscusses the best way to defend from these attacks using public cloud defenses, such as AmazonAWS, Google GCP, and Microsoft Azure, at a very low cost. Our mitigation strategy takes advantageof the fact that the attacker does not have full control to change the source IP port to anything theywant, when used in these reflective attacks. We propose to have the customer host their Web serversand other types of supporting servers in the public cloud. The cloud provider then reserves a /CIDRblock of IP addresses, which will be protected. The cloud providers customers who opt in, will beallocated an IP address from this block. This block will be used as the source IP address deny portionof the firewall rule-sets. Then the public cloud providers will use BGP4 Flow-Spec or some scriptingsolution, to have their IP service provider neighbors perform the actual filtering of the DRDoS attacktraffic concerning attacks against these servers.