> For the complete documentation index, see [llms.txt](https://waf-doc.inext.checkpoint.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://waf-doc.inext.checkpoint.com/how-to/how-to-protect-against-billion-laughs-attacks.md).

# How to Protect Against Billion Laughs Attacks

## Billion Laughs Attack Protection

A Billion Laughs attack is an XML denial-of-service technique where nested entity definitions expand exponentially in memory, crashing the parser. Unlike XXE, it uses only internal entities — no outbound call is made.

### How Check Point WAF Protects Against This

* **XXE Blocking** — natively blocks malicious DTD/entity abuse
* **Body Size Limit** — rejects oversized payloads before parsing begins, preventing entity expansion from consuming memory

### Configuration

Go to **WAF Portal → Your Application → Advanced Settings → Size Limits** and set:

* **Body Size (Kilobytes)** — keep this as low as your application allows
* **Max Object Depth** — limits XML/JSON nesting depth


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