rack-dedos

https://github.com/svoop/rack-dedos

Somewhat more radical filters designed to decimate malicious requests during a denial-of-service (DoS) attack by chopping their connection well before your Rack app wastes any significant resources on them – ouch! The filters have been proven to work against certain DoS attacks, however, they might also block IPs behind proxies or VPNs. Make sure you have understood how the filters are triggered and consider this middleware a last resort only to be enabled during an attack.