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Execution Chain Analysis
The attack follows this pattern:
`cmd.exe (BAT) ➡️ PowerShell ➡️ PowerShell ➡️ client32.exe ➡️ reg.exe`
Key Tactics:
- Uses client32.exe to execute NetSupport RAT
- Persists via reg.exe registry modifications
- Creates an `Options` folder in `%APPDATA%` if missing
- Downloads, extracts, and executes a malicious ZIP from `%APPDATA%\Application.zip`
- Deletes ZIP files post-execution for cleanup
You Should Know:
Detection & Hunting (KQL Query)
Use this Microsoft Defender XDR KQL query to hunt for similar BAT droppers:
DeviceProcessEvents
| where InitiatingProcessFileName =~ "cmd.exe"
| where FileName in~ ("powershell.exe", "client32.exe", "reg.exe")
| where ProcessCommandLine has_any ("%APPDATA%", "Application.zip")
| project Timestamp, DeviceName, FileName, ProcessCommandLine
Sandbox Analysis
- ANY.RUN Report: View Obfuscated BAT Dropper
Mitigation Commands
Windows:
Check for suspicious registry entries reg query HKCU\Software\Microsoft\Windows\CurrentVersion\Run /s | findstr "client32" Delete malicious files Remove-Item -Path "$env:APPDATA\Application.zip" -Force Remove-Item -Path "$env:APPDATA\Options" -Recurse -Force
Linux (Wine/Cross-Platform Analysis):
Monitor process chain (requires auditd) sudo auditctl -a exit,always -F arch=b64 -S execve -k bat_dropper Extract BAT script strings strings malicious.bat | grep -E "powershell|client32|reg.exe"
What Undercode Say
BAT droppers remain a low-tech but effective evasion method. Key takeaways:
1. Monitor `cmd.exe` spawning PowerShell with unusual arguments.
2. Block ZIP executions from `%APPDATA%` via AppLocker.
3. Audit registry modifications (`reg.exe`) post-PowerShell execution.
Prediction: Expect more multi-stage obfuscation combining BAT, PowerShell, and living-off-the-land binaries (LOLBins) like reg.exe.
Expected Output:
- Detected: `cmd.exe` → `powershell.exe` → `client32.exe`
- Mitigation: Registry cleanup + file deletion
- Hunting: KQL query + sandbox analysis
IT/Security Reporter URL:
Reported By: 0x534c Cybersecurity – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
