# Filter

***

### Filter Layer

After passing through the edge, traffic is forwarded to the filtering layer, which consists of **three sequential challenge stages** designed to effectively mitigate malicious traffic.

#### Dynamic Challenge Management

The challenge stages (**Cookie Challenge**, **PoW JS Challenge**, and **Custom Captcha**) are dynamically activated based on how many requests bypass the current filter level without being blocked. This allows for adaptive filtering depending on the current threat level and bot sophistication.

* The **threshold of allowed bypassed requests** before progressing to the next challenge stage is configurable via a **public API**.
* This ensures flexibility and allows tuning the filter aggressiveness depending on real-time attack patterns or sensitivity of protected content.

#### Challenge Stages:

1. **Cookie Challenge**\
   The cookie challenge is entirely invisible to users and supported by all modern web browsers as well as most HTTP libraries. It is a lightweight and effective method for defending against basic DDoS attacks without impacting the user experience.
2. **PoW JS Challenge**\
   The Proof-of-Work (PoW) JavaScript challenge is designed to block more advanced bots. It is slightly more intrusive, but still user-friendly. The difficulty of the challenge can be customized via api and provides a balance between protection and usability.
   * **Difficulty 6**: \~21.400 seconds
   * **Difficulty 5**: \~3.100 seconds
   * **Difficulty 4**: \~0.247 seconds
3. **Custom Captcha**\
   The custom captcha should be considered a last resort, or used to protect especially vulnerable or high-risk webpages. While highly effective, it has a more noticeable impact on user experience.

#### Information:

If a client fails too many challenges across the stages, their IP address will be dropped **at the edge level**, preventing further load on both the edge and the filter components.

### Clean Proxy

Once the filtering process is successfully completed, clean traffic is forwarded to the **clean proxy**, where it continues to the intended backend services.


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