nAspyUpdate

Hunt Hypothesis

The nAspyUpdate rule detects potential adversary behavior involving the execution of suspicious update processes that may be used to deploy malicious payloads or maintain persistence. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage compromise attempts that may evade traditional detection methods.

YARA Rule

rule nAspyUpdate : Family
{
    meta:
        description = "nAspyUpdate"
        author = "Seth Hardy"
        last_modified = "2014-07-14"
        
    condition:
        nAspyUpdateCode or nAspyUpdateStrings
}

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

• Scenario: Scheduled System Update via Windows Server Update Services (WSUS)
  Description: A legitimate system update is being deployed via WSUS, which triggers the nAspyUpdate rule.
  Filter/Exclusion: Check for process.name containing wsuapi.exe or wuauclt.exe, or filter by process.parent.name containing svchost.exe with WSUS in the command line.

• Scenario: Microsoft Endpoint Configuration Manager (MECM) Software Deployment
  Description: A software update is being pushed via MECM, which can trigger the nAspyUpdate rule.
  Filter/Exclusion: Use process.name containing ccmexec.exe or mpsvc.exe, or check for process.parent.name with taskeng.exe and MECM in the command line.

• Scenario: Microsoft Intune Policy Enforcement
  Description: A device compliance policy is being enforced by Intune, which may involve update checks or configuration changes.
  Filter/Exclusion: Filter by process.name containing intunewin.exe or microsoftedge.exe with Intune in the command line.

• Scenario: Admin Performing Manual Patch Installation
  Description: An administrator manually installs a patch using PowerShell or the command line, which may trigger the rule.
  Filter/Exclusion: Check for process.name containing powershell.exe with msu or msi in the command line, or filter by user field matching known admin accounts.

• Scenario: Antivirus or Endpoint Protection Scan
  Description: A scheduled scan by an antivirus or endpoint protection tool (e.g., Microsoft Defender, CrowdStrike) may trigger the nAspyUpdate rule.
  Filter/Exclusion: