Hunt Hypothesis
This detection rule identifies anomalous activity patterns associated with the “Yayih” indicator to uncover potential early-stage reconnaissance or lateral movement attempts within the Azure environment. Proactively hunting for these signals allows the SOC team to validate the efficacy of existing controls and correlate low-severity events that may otherwise be overlooked before escalating into significant incidents.
YARA Rule
rule Yayih : Family
{
meta:
description = "Yayih"
author = "Seth Hardy"
last_modified = "2014-07-11"
condition:
YayihCode or YayihStrings
}
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
Here are 5 specific false positive scenarios for the Yayih detection rule within an enterprise environment, including suggested filters and exclusions:
-
Scenario: Automated Backup Agent Scans
- Context: Enterprise backup solutions (e.g., Veeam Backup & Replication or Commvault) frequently perform deep file system scans on critical servers. These agents often execute high-volume read/write operations that mimic the behavioral patterns of the Yayih rule, particularly when scanning large databases or virtual machine images during peak business hours.
- Suggested Filter/Exclusion: Create an exclusion based on the specific process names of the backup agents (e.g.,
vbr.exe, simagent.exe) and restrict the alert to non-business hours if the scan is known to run overnight, or whitelist the specific source IP ranges of the backup management servers.
-
Scenario: Patch Management Deployment Cycles
- Context: During scheduled maintenance windows, patch management tools like Microsoft System Center Configuration Manager (SCCM) or Ivanti Endpoint Manager push updates to thousands of endpoints simultaneously. The mass installation and configuration changes triggered by these deployments can generate the specific event sequences that trigger the Yayih rule, often appearing as anomalous activity due to the sheer volume of concurrent connections.
- Suggested Filter/Exclusion: Implement a time-based filter to suppress alerts originating from known patch deployment windows (e.g., Sunday 02:00–06:00 UTC) and exclude events where the initiating user is a dedicated service account (e.g.,
svc-patch-deploy or DOMAIN\SCCM-Service).
-
Scenario: Identity & Access Management (IAM) Provisioning Jobs
- Context: Automated identity synchronization tasks using tools like Microsoft Entra ID (Azure AD) Connect or Okta Workforce Identity often