You are investigating whether an advanced persistent threat (APT) actor has operated in your organization's...

Comprehensive and Detailed 150 to 250 words of Explanation From Exact Extract Google Security Operations Engineer documents:

The core of this problem is the unreliable data quality for the file hash. A robust detection strategy cannot depend on an unreliable data point. Options B and C are weak because they create a dependency on the SHA256 hash, which the prompt states is "not reliably captured." This would lead to missed detections. Option A is far too broad and would generate massive noise.

The best detection engineering practice is to use the reliable IoCs in a flexible and high-performance manner. The domain is a reliable IoC (from DNS logs), and the hash is still a valuable IoC, even if it's only intermittently available.

The standard Google SecOps method for this is to create a List (referred to here as a "data table") containing both static IoCs: the hash and the domain. An engineer can then write a single, efficient YARA-L rule that references this list. This rule would trigger if either a PROCESS_LAUNCH event is seen with a hash in the list or a NETWORK_DNS event is seen with a domain in the list (e.g., (event.principal.process.file.sha256 in %ioc_list) or (event.network.dns.question.name in %ioc_list)). This creates a resilient detection mechanism that provides two opportunities to identify the threat, successfully working around the unreliable data problem.

(Reference: Google Cloud documentation, "YARA-L 2.0 language syntax"; "Using Lists in rules"; "Detection engineering overview")