Malicious ClickFix Execution Chain Spawning MSHTA via Pcalua on EtherRAT Infection

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
- T1218System Binary Proxy Execution
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the Program Compatibility Assistant launcher pcalua.exe being abused to proxy execution of mshta.exe against an HTML application. This living-off-the-land chain is a ClickFix step in the EtherRAT SYS_INFO campaign that fetches command and control from an Ethereum contract. Using pcalua to break the parent-child chain evades detections keyed on direct mshta launches.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

Windows Process Creation: Suspicious Children Spawned by HTML Help (hh.exe)

Windows: Alert on Suspicious HH.EXE Process Execution

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Malicious Script Host Spawning PowerShell With Invoke-Expression (via process_creation)

Hidden PowerShell Archive Extraction via ExtractToDirectory

CastleLoader ClickFix PowerShell Hex Decode and Re-Execution

Suspicious Cabinet Extraction of Masqueraded vstm Archive via extrac32

Malicious Non-Interactive Encoded PowerShell Stager (via process_creation)

Malicious ClickFix Execution Chain Spawning MSHTA via Pcalua on EtherRAT Infection

Pivot detection · T1059.001 · 9 related

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