This rule detects the execution of the specific binary or script artifact ‘yzpackV11UsAr’, which may indicate an adversary deploying a custom tool or payload for initial access or lateral movement. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify low-severity anomalies that could serve as early precursors to more complex attack chains before they escalate in severity.
rule yzpackV11UsAr
{
meta:
author="malware-lu"
strings:
$a0 = { 60 33 C0 8D 48 07 50 E2 FD 8B EC 64 8B 40 30 78 0C 8B 40 0C 8B 70 1C AD 8B 40 08 EB 09 8B 40 34 8D 40 7C 8B 40 3C 89 45 04 E8 F3 07 00 00 60 8B 5D 04 8B 73 3C 8B 74 33 78 03 F3 56 8B 76 20 03 F3 33 C9 49 92 41 AD 03 C3 52 33 FF 0F B6 10 38 F2 }
condition:
$a0 at pe.entry_point
}This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Legitimate Application Deployment via Group Policy: When IT administrators deploy a new version of a line-of-business application (e.g., Adobe Creative Cloud, Microsoft Office, or internal ERP clients) using Group Policy Objects (GPOs) or SCCM, the installer may execute a background service or helper process named yzpackV11UsAr to handle licensing, telemetry, or component registration.
gpupdate.exe, ccmexec.exe, or msiexec.exe and the execution path resides within standard application directories (e.g., C:\Program Files\, C:\Program Files (x86)\) or the C:\Windows\Installer folder.Scheduled Maintenance Task for Database Indexing: A scheduled task (Task Scheduler) runs nightly to optimize or rebuild indexes for a local SQL Server or PostgreSQL instance. The maintenance utility may spawn a temporary worker process or helper script named yzpackV11UsAr to manage lock states or temporary file cleanup.
schtasks.exe or svchost.exe (specifically the Tasks service) and the working directory is within the database engine’s binary path (e.g., C:\Program Files\Microsoft SQL Server\ or C:\Program Files\PostgreSQL\).Antivirus/EDR Self-Update or Scan Component: During a full system scan or a scheduled definition update, the security suite (e.g., CrowdStrike Falcon, Microsoft Defender, or SentinelOne) may instantiate a short-lived helper process or cache cleaner named yzpackV11UsAr to manage quarantine logs or update staging files.