DNS software and service providers will update their DNS software to speed up DNS traffic and fight against DDoS attacks by stopping the implementation of DNS resolver workarounds still used by numerous DNS authoritative systems. The change will be added by major resolver vendors (i.e., ISC, CZ NIC, NLNET Labs, PowerDNS) to their open source DNS resolvers. DNS flood and DNS amplification attacks are most probably the main culprits, although cache and fast flux DNS attacks, among others, may also be affected by future changes in DNS software.
Source: https://www.bleepingcomputer.com/news/security/dns-ddos-attack-protections-to-be-forcefully-enabled-for-non-compliant-sites/