---
description: Enable automatic mitigation of random prefix attacks in the Cloudflare dashboard or via the API.
title: Setup
image: https://developers.cloudflare.com/og-docs.png
---

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# Setup

Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/dns/dns-firewall/random-prefix-attacks/setup/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/)

In order to enable automatic mitigation of [random prefix attacks](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/dns/dns-firewall/random-prefix-attacks/about/):

1. Set up [DNS Firewall](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/dns/dns-firewall/setup/).
2. Enable attack mitigation on your DNS Firewall cluster.

  1. In the Cloudflare dashboard, go to the **DNS Firewall Clusters** page.  
  [Go to **Clusters** ↗](https://dash.cloudflare.com/?to=/:account/dns-firewall/clusters)
  2. Select the cluster you want to update, then select **Edit**.
  3. Turn on **Attack mitigation** and choose whether Cloudflare should only mitigate attacks when the upstream is unhealthy.
  4. Select **Save**.  
Send a [PATCH request](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/api/resources/dns%5Ffirewall/methods/edit/) to update your DNS Firewall cluster:  
Required API token permissions  
At least one of the following [token permissions](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/fundamentals/api/reference/permissions/) is required:
  * `DNS Firewall Write`  
```bash  
curl "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/dns_firewall/$DNS_FIREWALL_ID" \
	--request PATCH \
	--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
	--json '{  
		"attack_mitigation": {  
				"enabled": true,  
				"only_when_upstream_unhealthy": true  
		}  
	}'  
```

Once you turn on attack mitigation, Cloudflare returns a `REFUSED` response to queries that are part of a random prefix attack.

Note

If you do not specify otherwise, Cloudflare automatically sets the `only_when_upstream_unhealthy` parameter to true, which means that Cloudflare will only mitigate attacks when we detect that the upstream is unresponsive (possibly as a result of an attack).

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