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The Block responder returns a 403 Forbidden status code with an “Access denied” message, immediately terminating the request from matching IP ranges.

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Overview

This is the simplest responder type - it sends a standard HTTP 403 response to any client from a blocked IP range. No additional configuration is required beyond specifying which IP ranges to block.

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Configuration

The Block responder requires no additional parameters beyond the standard ranges configuration.
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ranges
string[]
IP ranges to block. Can be CIDR notations (e.g., 192.168.1.0/24) or predefined service keys (e.g., openai, aws, gcloud).Default: ["aws", "azurepubliccloud", "deepseek", "gcloud", "githubcopilot", "openai"]
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whitelist
string[]
Optional list of specific IP addresses to exclude from blocking, even if they match the ranges.Note: Only supports individual IP addresses, not CIDR ranges.Default: []

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HTTP Response

When a client from a blocked range makes a request:
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status
number
403
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body
string
Access denied
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Content-Type
string
text/plain

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Examples

localhost:8080 {
    defender block {
        ranges openai aws deepseek
    }
    respond "Human-friendly content"
}

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Implementation Details

The Block responder is implemented in responders/block.go:12: 
func (b BlockResponder) ServeHTTP(w http.ResponseWriter, _ *http.Request, _ caddyhttp.Handler) error {
    w.WriteHeader(http.StatusForbidden)
    _, err := w.Write([]byte("Access denied"))
    return err
}
The response is immediate with no delay or additional processing.

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Use Cases

  • Block AI Scrapers: Prevent AI companies from scraping your content
  • Geo-blocking: Block specific geographic regions (when combined with region-specific ranges)
  • Known Bad Actors: Block IPs from known malicious sources
  • Cloud Provider Restrictions: Prevent access from specific cloud providers

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Comparison with Other Responders

  • vs Custom: Block always returns 403, while Custom allows any status code and message
  • vs Drop: Block sends a proper HTTP response, while Drop terminates the connection
  • vs Tarpit: Block responds immediately, while Tarpit deliberately slows down the response
  • vs Garbage: Block returns a clear error, while Garbage returns meaningless data

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