Denial of Service

What It Means

This request either matched a pattern identified as initiating a Denial of Service (DoS) attack or originates from a source that has previously been involved in an attack.

Why It Matters

Denial of service attacks aim to overwhelm your application with traffic, making it unavailable to legitimate users. Even a moderate-volume attack can exhaust your Heroku dyno resources and cause timeouts for real visitors.

Common Triggers

Extremely high request rates from a single source, traffic patterns matching known DoS tools, or requests from IP addresses that have participated in recent distributed attacks.

What To Do

These blocks are critical for keeping your application available. If you are experiencing a sustained attack and want additional protection, see DDoS HTTP Flood Protection for more options. If a legitimate high-traffic source is being blocked (such as a load testing tool), run your tests from an allowlisted IP.