A number of companies offer DDoS protection for websites at an additional cost. These services are called CDNs, or content delivery networks, and can be used by people self-hosting their site or using a shared hosting service. Many hosted services implement these or similar DDoS protection measures. While they can be expensive, services like this can offer the best available protection against a DDoS attack.

Such services include (but are not limited to) the following:

DDoS protection services Sites
Akamai https://www.akamai.com/us/en/resources/protect-against-ddos-attacks.jsp
Arbor Networks https://www.arbornetworks.com/ddos-protection-products/arbor-aps
Cloudflare https://www.cloudflare.com/ddos/
Fastly https://www.fastly.com/
Imperva Incapsula https://www.incapsula.com/ddos-protection-services.html
Neustar https://www.neustar.biz/security/ddos-protection
NexusGuard https://www.nexusguard.com/
Verisign https://www.verisign.com/en_US/security-services/ddos-protection/index.xhtml

A handful of services are available for free to eligible individuals and groups:

Cloudflare’s Project Galileo https://www.cloudflare.com/galileo/
Deflect https://deflect.ca/
Google’s Project Shield https://projectshield.withgoogle.com/public/
Qurium/VirtualRoad.org https://www.qurium.org/services/