Themida10xx1800compressedengineOreansTechnologies

Hunt Hypothesis

This rule identifies the presence of binaries protected by the Themida 10.x.x.1800 compression engine, a technique frequently employed by adversaries to obscure code execution and evade static analysis. Proactively hunting for these signatures in Azure Sentinel allows the SOC to detect potentially obfuscated malware or custom tools that may be leveraging commercial packers to hide their true intent within the environment.

YARA Rule

rule Themida10xx1800compressedengineOreansTechnologies
{
      meta:
		author="malware-lu"
strings:
		$a0 = { B8 [4] 60 0B C0 74 58 E8 00 00 00 00 58 05 43 00 00 00 80 38 E9 75 03 61 EB 35 E8 00 00 00 00 58 25 00 F0 FF FF 33 FF 66 BB 19 5A 66 83 C3 34 66 39 18 75 12 0F B7 50 3C 03 D0 BB E9 44 00 00 83 C3 67 39 1A 74 07 2D 00 10 00 00 EB DA 8B F8 B8 }
	$a1 = { B8 [4] 60 0B C0 74 58 E8 00 00 00 00 58 05 43 00 00 00 80 38 E9 75 03 61 EB 35 E8 00 00 00 00 58 25 00 F0 FF FF 33 FF 66 BB 19 5A 66 83 C3 34 66 39 18 75 12 0F B7 50 3C 03 D0 BB E9 44 00 00 83 C3 67 39 1A 74 07 2D 00 10 00 00 EB DA 8B F8 B8 [4] 03 C7 B9 5A [3] 03 CF EB 0A B8 [4] B9 5A [3] 50 51 E8 84 00 00 00 E8 00 00 00 00 58 2D 26 00 00 00 B9 EF 01 00 00 C6 00 E9 83 E9 05 89 48 01 61 E9 AF 01 }

condition:
		$a0 at pe.entry_point or $a1 at pe.entry_point
}

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

This rule contains 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Legitimate Commercial Software Updates (e.g., Adobe Creative Cloud, JetBrains IDEs)

  • Scenario: Many commercial applications use Themida for code obfuscation and anti-tampering. When these apps perform background updates or launch helper processes, the compressed engine signature may be detected in the binary or its in-memory state.
  • Filter/Exclusion: Exclude processes where the parent process is a known installer or updater (e.g., AdobeUpdate.exe, JetBrainsUpdater.exe) or filter by specific image paths (e.g., C:\Program Files\Adobe\, C:\Program Files\JetBrains\).

• Game Launchers and Anti-Cheat Services (e.g., Steam, Epic Games, Riot Client)

  • Scenario: Game launchers and their associated anti-cheat or overlay services often use obfuscation to protect proprietary logic. During game launch, the launcher may spawn child processes that contain the Themida-compressed engine, triggering the rule.
  • Filter/Exclusion: Exclude processes whose parent is a known game launcher (e.g., steam.exe, EpicGamesLauncher.exe, RiotClient.exe) or filter by specific service names (e.g., RiotClientServices.exe, SteamWebHelper.exe).

• Virtual Machine and Container Image Extraction (e.g., VMware, Docker, Hyper-V)

  • Scenario: When extracting or mounting virtual machine images or container layers, the underlying binaries (often from Windows guest OSes or specific applications) may be scanned. If the guest OS contains Themida-protected software, the extraction process or the mounted binaries can trigger the detection.
  • Filter/Exclusion: Exclude processes related to virtualization management (e.g., vmware-vmx.exe, dockerd.exe, svchost.exe with specific service names