Linux Syscall Threat Detection in Splunk with Uncoder AI

How It Works

The detection logic here is built around monitoring use of the mknod syscall, which is rarely used in legitimate workflows but can be exploited by attackers to:

• Create fake block or character devices
  
• Interact with kernel interfaces
  
• Bypass file system controls or establish backdoors

Left Panel – Sigma Rule:

• Logsource: auditd on Linux
  
• Focuses on syscall: mknod
  
• Tagged with MITRE technique T1543.003 (Create or Modify System Process: Linux and Mac Startup Items)
  

False positives include device initialization by tools like udevadm or MAKEDEV

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Right Panel – Splunk SPL Translation:

Uncoder AI generates the corresponding SPL:

index=linux (type="SYSCALL" AND syscall="mknod")

This query is minimal yet accurate — targeting syscall audit events with exact field matching for mknod, ready to be deployed in a Splunk environment with Linux audit log ingestion.

Why It’s Innovative

Cross-platform telemetry translation from Sigma to Splunk SPL is non-trivial due to:

• Field mapping between abstract Sigma keys and Splunk’s indexed data fields
  
• Syntax differences (SPL’s AND, quotes, field=value matching)
  
• Understanding the target telemetry (auditd → SYSCALL type logs)
  

Uncoder AI handles these challenges automatically by:

• Mapping field names and values to Splunk conventions
  
• Preserving detection semantics from the original Sigma logic
  
• Ensuring compatibility with default or custom Splunk schemas

Operational Value

For detection teams and security operations centers:

• Instant deployment of Sigma threat content into Splunk SIEM
  
• Improved Linux telemetry coverage for low-frequency, high-risk behavior
  
• Enhanced detection for persistence techniques and covert channel creation
  
• Reduced engineering effort, allowing teams to stay focused on investigations
  

Uncoder AI bridges open threat content and proprietary platforms like Splunk, making it easy to implement sophisticated Linux detections like mknod monitoring in real time.

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