This detection identifies potential fileless or polyglot malware activity where adversaries execute suspicious code structures that may evade traditional signature-based defenses by leveraging the SimbiOZPoly21Extranger YARA rule. A proactive hunt in Azure Sentinel is essential to uncover early-stage lateral movement or command-and-control communications from these low-severity anomalies before they escalate into significant security incidents within the cloud environment.
rule SimbiOZPoly21Extranger
{
meta:
author="malware-lu"
strings:
$a0 = { 55 50 8B C4 83 C0 04 C7 00 [4] 58 C3 90 }
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.
Here are 4 specific false positive scenarios for the SimbiOZPoly21Extranger detection rule, including targeted filters and exclusions:
Antivirus Real-Time Scanning of Compressed Archives
.7z or .zip archives containing mixed file types. When the scanner extracts and scans these polyglot files, the YARA rule may misinterpret the embedded metadata or nested structures as the “Extranger” signature.C:\Program Files\CrowdStrike\csagent.exe (or equivalent AV service names) when the file extension is .7z, .zip, or .tar. Add a rule condition to ignore alerts where the parent process is the known AV scanner.Scheduled Software Deployment via SCCM/Intune
.msi containing embedded scripts and resources). The deployment agent extracts these components to a temporary staging folder (C:\Windows\CCMCache), triggering the rule due to the complex file structure.C:\Windows\CCMCache\* and processes named ccmsetup.exe or Microsoft.IntuneManagementAgent. Additionally, suppress alerts occurring during the defined maintenance window (e.g., 02:00 – 04:00 UTC).Backup Agent Processing of Virtual Machine Snapshots