No, it won’t protect from bad attack like DDoS. However, Cloudflare DNS is still secure than most. It offers DNSSEC protection.
What Is DNSSEC?
Like many internet protocols, the DNS system was not designed with security in mind and contains several design limitations. These limitations, combined with advances in technology, have made it easy for attackers to hijack a DNS lookup for malicious purposes, such as sending a user to a fraudulent website that can distribute malware or collect personal information. The DNS Security Extensions (DNSSEC) is a security protocol created to mitigate this problem. DNSSEC protects against attacks by digitally signing data to help ensure its validity. In order to ensure a secure lookup, the signing must happen at every level in the DNS lookup process.
For DDoS or Brute force protection, you should prefer Sucuri Web Firewall services.
Or, opt for Cloudflare Pro/Business plan.