This hypothesis targets the presence of the Armadillo malware family, a known threat actor toolset often used for initial access and lateral movement, by scanning for its specific YARA signature across Azure Sentinel workloads. Proactively hunting for this low-severity indicator allows the SOC team to identify dormant or early-stage infections before they escalate into more complex post-exploitation activities or data exfiltration events.
rule Armadillov253b3
{
meta:
author="malware-lu"
strings:
$a0 = { 55 8B EC 6A FF 68 D8 [3] 68 14 [3] 64 A1 [4] 50 64 89 25 [4] 83 EC 58 53 56 57 89 65 E8 FF 15 }
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.
Scenario: A security team or developer is actively testing the “Armadillo” malware family (or a similar APT tool) in an isolated lab environment or a dedicated test segment of the network. The YARA rule scans memory dumps or process binaries and matches the specific signature of the tool during active analysis.
Environment: Lab or Role: Security Testing from this specific YARA scan, or whitelist the specific process names (e.g., armadillo_test.exe) if they are known to be running under a controlled user account.Scenario: An enterprise endpoint protection platform (EPP) or anti-malware solution (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) is performing a full system scan or on-access scanning. The YARA engine is integrated into the EPP and matches the signature against legitimate files that contain similar code patterns or are being temporarily written to disk during a patch deployment.
csagent.exe, MsMpEng.exe) and ensure the file path is within the EPP’s quarantine or temporary scan directories (e.g., C:\ProgramData\Microsoft\Windows Defender\Quarantine\).Scenario: A custom in-house application or a third-party software update package (e.g., a .NET assembly or a C++ binary) contains a code block or string literal that inadvertently matches the byte pattern defined in the Armadillov253b3 YARA rule. This often happens if the rule uses a generic string match (like a specific GUID or function name) that is also used by legitimate vendor software.