Quarian

Hunt Hypothesis

This detection rule identifies anomalous activity associated with the “Quarian” indicator, which may signal early-stage reconnaissance or lateral movement by an adversary within the Azure environment. Proactively hunting for this behavior allows the SOC team to validate potential low-severity signals before they escalate into significant incidents, ensuring comprehensive visibility across cloud assets.

YARA Rule

rule Quarian : Family
{
    meta:
        description = "Quarian"
        author = "Seth Hardy"
        last_modified = "2014-07-09"
        
    condition:
        QuarianCode or QuarianStrings
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints
• Source Rule

False Positive Guidance

Based on the context of SOC operations and the rule name “Quarian” (which typically refers to Microsoft Defender for Cloud Apps or similar cloud access security rules monitoring user behavior, specifically regarding unfamiliar sign-in locations, new device usage, or high-risk application access), here are 5 specific false positive scenarios in a legitimate enterprise environment:

• Scheduled Infrastructure Patching by IT Operations

  • Scenario: The “Quarian” rule triggers an alert for “Unusual Sign-in Location” when the automated patch management system (e.g., Microsoft Endpoint Configuration Manager (MECM) or Ivanti) connects to the cloud tenant from a centralized data center IP range that is distinct from standard user office locations. This often happens during off-hours maintenance windows where the service account performs bulk updates across multiple regions.
  • Filter/Exclusion: Create an exclusion rule based on the specific Service Account Identity (e.g., [email protected]) and whitelist the static IP addresses of the patch management servers in the detection logic.

• Enterprise SaaS Migration via Managed Service Providers (MSP)

  • Scenario: During a quarterly migration project, an external MSP partner uses tools like Tenable or ServiceNow to provision new user accounts and configure security policies. The rule flags these activities as “New Device” or “Impossible Travel” because the MSP engineers are accessing the tenant from their own corporate network (a different geo-location) using a shared jump-host device, which differs from the standard employee baseline.
  • Filter/Exclusion: Implement an exclusion for traffic originating from known MSP Partner IP Ranges and tag these sessions with a specific User-Agent string containing “MSP-Managed” to bypass the location anomaly check.

• Automated Backup and Compliance Reporting Jobs

  • **Scenario