PowerShell Hidden DownloadString Execution via ClickFix Fake CAPTCHA (via process_creation)

ATT&CK techniques

Execution → C2

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1105Ingress Tool Transfer
Exfiltration
Impact

What it detects

This rule detects PowerShell invoked with hidden window and bypassed execution policy to download and execute a remote script through DownloadString, the second stage delivered by a Lumma Stealer fake CAPTCHA ClickFix lure. Combining hidden execution with an inline remote DownloadString call outside the browser context is a common precursor to stealer deployment.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

Suspicious PowerShell Hidden Download Cradle via IEX

Suspicious PowerShell WebClient DownloadString Payload Retrieval via Script (via ps_script)

Suspicious PowerShell Download of Disguised Payload to ProgramData

Suspicious PowerShell WebClient Download of Executable Payload

Suspicious PowerShell Remote Script Execution via IEX DownloadString

Suspicious PowerShell Download Cradle to Blogspot (via process_creation)

Suspicious Hidden PowerShell WebClient DownloadFile Cradle

Suspicious PowerShell Download Cradle with Spoofed User-Agent via MSIX

Malicious PowerShell In-Memory Download Cradle via Script Block (via ps_script)

PowerShell Hidden DownloadString Execution via ClickFix Fake CAPTCHA (via process_creation)

Pivot detection · T1059.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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