[Gateway] How sandboxing works (#17743)

Author: maxvp

src/content/docs/cloudflare-one/policies/gateway/http-policies/file-sandboxing.mdx

@@ -13,7 +13,37 @@ Only available on Enterprise plans. For more information, contact your account t
 
 In addition to [anti-virus (AV) scanning](/cloudflare-one/policies/gateway/http-policies/antivirus-scanning/), Gateway can quarantine previously unseen files downloaded by your users into a sandbox and scan them for malware.
 
-While the files are quarantined, Gateway will present a scanning page to your users. If a file passes scanning, Gateway will release the file from quarantine and download it to your user's device. If the file contains malware, Gateway will block the request and log the match as a Block decision in your [HTTP logs](/cloudflare-one/insights/logs/gateway-logs/#http-logs).
+If AV scanning does not detect malware in a file download, Gateway will quarantine the file in the sandbox. If the file has not been downloaded before, Gateway will monitor any actions taken by the file and compare them to known malware patterns. During this process, Gateway will display an interstitial page in the user's browser. If the sandbox does not detect malicious activity, Gateway will release the file from quarantine and download it to your user's device. If the sandbox detects malicious activity, Gateway will block the download. For any subsequent downloads of the file, Gateway will remember and apply its allow/block decision.
+
+Gateway will log any file sandbox decisions in your [HTTP logs](/cloudflare-one/insights/logs/gateway-logs/#http-logs).
+
+```mermaid
+flowchart TD
+    A(["User starts file download"]) --> B["File sent to AV scanner"]
+    B --> C["Malicious file detected?"]
+    C -- Yes --> D["Download blocked"]
+    C -- No --> G["File sent to sandbox"]
+    G --> n1["First time file downloaded?"]
+    K["Malicious activity detected?"] -- Yes --> N["Download blocked"]
+    K -- No --> n3["Download allowed"]
+    n2["Interstitial page displayed for user during scan"] --> n4["File activity monitored"]
+    n1 -- Yes --> n2
+    n4 --> K
+    n1 -- No --> K
+
+    B@{ shape: subproc}
+    C@{ shape: hex}
+    D@{ shape: terminal}
+    n1@{ shape: hex}
+    K@{ shape: hex}
+    N@{ shape: terminal}
+    n3@{ shape: terminal}
+    n2@{ shape: display}
+    n4@{ shape: rect}
+    style D stroke:#D50000
+    style N stroke:#D50000
+    style n3 stroke:#00C853
+```
 
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