Splice11byTw1stedL0gic

Hunt Hypothesis

This rule detects the presence of the Splice11byTw1stedL0gic YARA signature, which likely identifies a specific malicious script, memory artifact, or low-level code pattern associated with a particular threat actor or tooling. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify early-stage footholds or dormant payloads that may not yet trigger high-severity alerts, enabling faster containment of targeted intrusions.

YARA Rule

rule Splice11byTw1stedL0gic
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 68 00 1A 40 00 E8 EE FF FF FF 00 00 00 00 00 00 30 00 00 00 40 00 00 00 00 00 00 00 [16] 00 00 00 00 00 00 01 00 00 00 [6] 50 72 6F 6A 65 63 74 31 00 [7] 00 00 00 00 06 00 00 00 AC 29 40 00 07 00 00 00 BC 28 40 00 07 00 00 00 74 28 40 00 07 00 00 00 2C 28 40 00 07 00 00 00 08 23 40 00 01 00 00 00 38 21 40 00 00 00 00 00 FF FF FF FF FF FF FF FF 00 00 00 00 8C 21 40 00 08 ?? 40 00 01 00 00 00 AC 19 40 00 00 00 00 00 00 00 00 00 00 00 00 00 AC 19 40 00 4F 00 43 00 50 00 00 00 E7 AF 58 2F 9A 4C 17 4D B7 A9 CA 3E 57 6F F7 76 }

condition:
		$a0 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 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A DevOps engineer uses Terraform or Ansible to provision a new Kubernetes cluster, where the control plane nodes are configured to use a custom CoreDNS plugin or a specific Service Mesh sidecar (e.g., Istio) that injects a unique binary or configuration file matching the YARA signature.
  • Filter/Exclusion: Exclude processes or files located in standard container runtime paths (e.g., /var/lib/docker/containers/, /var/lib/kubelet/pods/) or match against known container image digests.
• Scenario: An IT administrator performs a scheduled Windows Update or Cumulative Patch installation via WSUS (Windows Server Update Services), where the update package contains a new system DLL or driver that inadvertently matches the “Splice11” logic due to a specific code pattern in the patch metadata or binary structure.
  • Filter/Exclusion: Exclude events where the parent process is wuaexer.exe (Windows Update Agent) or TrustedInstaller.exe, or filter by file paths under C:\Windows\SoftwareDistribution\ and C:\Windows\WinSxS\.
• Scenario: A security team runs a Vulnerability Scanner (e.g., Qualys or Tenable Nessus) on a web server, which executes a small probe script or agent to check for specific library versions. The probe may use a spliced or obfuscated string to test for known CVEs, triggering the YARA rule if the rule targets specific string splicing techniques.
  • Filter/Exclusion: Exclude processes running from the scanner’s agent directory (e.g., C:\Program Files\Qualys\Agent\ or /opt/qualys/agent/) or match against the scanner’s service name (e.g.,