In ZIA, user traffic is first forwarded to a Zscaler Enforcement Node (ZEN), where security and access policies are enforced and transaction logs are generated. Those logs are then sent from the ZEN to the cloud-based Nanolog cluster, which is the highly scalable logging and storage layer used by Zscaler. Nanolog compresses and stores the logs for reporting, analytics, and long-term retention.
To deliver logs to a customer’s SIEM, the Nanolog Streaming Service (NSS) is deployed in the customer environment. NSS establishes a secure, outbound tunnel to the Nanolog service in the Zscaler cloud and subscribes to that customer’s log stream. Nanolog then continuously streams a copy of relevant logs over this secure connection to NSS. NSS receives the logs, converts them into the required output format (for example, syslog or CEF), and forwards them on to the configured SIEM or log receiver.
Option C is the only answer that correctly represents the logical sequence: user traffic through ZEN, ZEN to Nanolog, secure tunnel from NSS, Nanolog streaming to NSS, and finally NSS forwarding to the SIEM.
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