Inside SynkLoader: A Loader Packed with Evasion Techniques

Summary

SynkLoader is a newly identified modular malware family that uses a multi-language architecture to complicate detection. The malware relies on a Python-based loader to deploy memory-resident modules for system profiling, persistence, and credential theft through a fake Windows lock screen. It also uses advanced evasion techniques including in-memory DLL loading and custom ChaCha20 encryption for C2 communications.

Investigation

Researchers discovered SynkLoader during an incident investigation and later built a C2 emulator to draw the threat actors into a controlled environment. By supplying fake system information, they observed the deployment of multiple modules, including persistence and phishing components. This active deception approach allowed analysts to capture a large portion of the attacker’s toolkit and better understand its communication protocols.

Mitigation

Organizations should block unauthorized MSI installers delivered from public cloud storage and monitor for suspicious PowerShell activity involving encoded commands. Strict controls around Microsoft Teams file downloads and monitoring for unauthorized scheduled tasks created through COM interfaces are recommended. EDR solutions should also detect in-memory DLL loading and unusual Python process behavior.

Response

If SynkLoader activity is detected, the affected host should be isolated immediately to limit lateral movement enabled by the TrafficRedirector module. Responders should perform memory forensics to identify resident components and inspect scheduled tasks or COM object manipulation for persistence. Authentication logs should also be reviewed for suspicious sign-ins following possible deployment of the PhishLocker module.

Simulation Execution

Prerequisite: The Telemetry & Baseline Pre-flight Check must have passed.

Rationale: This section details the precise execution of the adversary technique (TTP) designed to trigger the detection rule. The commands and narrative MUST directly reflect the TTPs identified and aim to generate the exact telemetry expected by the detection logic. Abstract or unrelated examples will lead to misdiagnosis.

• Attack Narrative & Commands: An adversary has gained initial access and intends to execute a secondary-stage payload entirely in memory to avoid leaving a footprint on the disk. To evade simple file-based AV, they use PowerShell’s Invoke-Expression (aliased as iex) to run a hex-encoded string. They also attempt to use the [System.Management.Automation.ScriptBlock]::Create method, a more advanced technique often used by sophisticated loaders to execute code blocks directly from memory. These actions are designed to trigger the specific command-line patterns monitored by the security rule.

• Regression Test Script:

  # Simulation Script: Triggering In-Memory Execution Detection
  Write-Host "[*] Starting Detection Validation Simulation..." -ForegroundColor Cyan
  
  # 1. Trigger via 'iex' (Invoke-Expression)
  Write-Host "[*] Executing Payload via 'iex' pattern..." -ForegroundColor Yellow
  $hexPayload = "Write-Host 'ALARM: In-memory execution via IEX detected!'"
  $hexEncoded = [System.BitConverter]::ToString([System.Text.Encoding]::UTF8.GetBytes($hexPayload)).Replace("-", " ")
  # Simulating the command line execution that would appear in logs
  powershell.exe -Command "iex ([System.Text.Encoding]::UTF8.GetString([System.Convert]::FromHexString('$($hexEncoded.Replace(' ', ''))')))"
  
  Start-Sleep -Seconds 2
  
  # 2. Trigger via 'ScriptBlock::Create' pattern
  Write-Host "[*] Executing Payload via 'ScriptBlock::Create' pattern..." -ForegroundColor Yellow
  $cmd = "Write-Host 'ALARM: In-memory execution via ScriptBlock detected!'"
  powershell.exe -Command "& ([System.Management.Automation.ScriptBlock]::Create('$cmd'))"
  
  Write-Host "[*] Simulation Complete." -ForegroundColor Green

• Cleanup Commands:

  # No persistent artifacts are created by this simulation as it is purely in-memory.
  # However, we clear the console to signify completion.
  Clear-Host
  Write-Host "[*] Cleanup Complete. No files were written to disk." -ForegroundColor Cyan