Security-Operations-Engineer Exam Dumps : Google Cloud Certified - Professional Security Operations Engineer (PSOE) Exam

This YARA-L rule is designed to correlate a real-time event (a DNS query, $dns) with known-bad indicators stored in the Google SecOps entity graph ($ioc). The code must correctly filter the entity graph to find the specific indicators from the custom MISP feed.

Two filters are required:

$ioc.graph.metadata.entity_type = "DOMAIN_NAME": This line is essential to filter the entity graph for IoCs that are domains. The rule is trying to match a DNS query ($dns_query) to a known C2 domain, so the entity type must be DOMAIN_NAME.

$ioc.graph.metadata.source_type = "ENTITY_CONTEXT": This is the key differentiator. The Google SecOps entity graph has multiple context sources. GLOBAL_CONTEXT (Option B) is for threat intelligence provided by Google (e.g., Google Threat Intelligence, Mandiant). DERIVED_CONTEXT (Option C) is for context inferred from UDM events. The prompt explicitly states the IoC feed is the organization's own "threat intelligence feed... ingested... with... MISP." This type of customer-provided, third-party intelligence is classified as ENTITY_CONTEXT. Adding this line ensures the rule only uses the custom MISP feed for its IoC data, as intended.

The other lines in the $ioc block, such as product_name = "MISP", further refine this ENTITY_CONTEXT search.

(Reference: Google Cloud documentation, "YARA-L 2.0 language syntax"; "Context-aware detections with entity graph"; "Populate the entity graph")

The most reliable, automated, and low-maintenance solution is to use the native Google Security Operations (SecOps) SOAR capabilities. A playbook block is a reusable, automated workflow that can be attached to other playbooks, such as the standard case closure playbook.

This block would be configured with a conditional action. This action would check a case field (e.g., case.escalation_status == "escalated"). If the condition is true, the playbook automatically proceeds down the "Yes" branch, which would use an integration action (like "Send Email" for Gmail or Outlook) to send the case details to the director. After the email action, it would proceed to the "Close Case" action. If the condition is false (the case was not escalated), the playbook would proceed down the "No" branch, which would skip the email step and immediately close the case.

This method ensures the process is "reliably sent" and "automatic," as it's built directly into the case management logic. Options C and D are incorrect because they rely on manual analyst actions, which are not reliable and violate the "automatic" requirement. Option A is a custom, external solution that adds unnecessary complexity and maintenance overhead compared to the native SOAR playbook functionality.

(Reference: Google Cloud documentation, "Google SecOps SOAR Playbooks overview"; "Playbook blocks"; "Using conditional logic in playbooks")

Comprehensive and Detailed Explanation

The correct solution is Option B. This is a common false positive tuning scenario.

The "high priority network indicators" rule set triggers when it sees a connection to or from a known-malicious IP or domain. The problem states the false positives are coming from the on-premises proxy servers.

This implies that the proxy server itself is initiating traffic that matches these indicators. This is often benign, legitimate behavior, such as:

Resolving a user-requested malicious domain via DNS to check its category.

Performing an HTTP HEAD request to a malicious URL to scan it.

Fetching its own threat intelligence or filter updates.

In all these cases, the source of the network connection is the proxy server. In the Unified Data Model (UDM), the source IP of an event is stored in the principal.ip field.

To eliminate these false positives, you must create a rule exclusion (or add a not condition to the rule) that tells the detection engine to ignore any events where the principal.ip is the IP address of your trusted proxy servers. This will not affect the rule's ability to catch a workstation behind the proxy (whose IP would be the principal.ip) connecting through the proxy to a malicious target.ip.

Exact Extract from Google Security Operations Documents:

Curated detection exclusions: Curated detections can be tuned by creating exclusions to reduce false positives from known-benign activity. You can create exclusions based on any UDM field.

Tuning Network Detections: A common source of false positives for network indicator rules is trusted network infrastructure, such as proxies or DNS servers. This equipment may generate traffic to malicious domains or IPs as part of its normal operation (e.g., DNS resolution, content filtering lookups). In this scenario, the traffic originates from the infrastructure device itself. To filter this noise, create an exclusion where the principal.ip field matches the IP address (or IP range) of the trusted proxy server. This prevents the rule from firing on the proxy's administrative traffic while preserving its ability to detect threats from end-user systems.