Malicious Interlock RAT FileFix Download-Cradle via PowerShell WebClient with PowerShell User-Agent (via ps_script)

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
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects the KongTuke FileFix PowerShell cradle that sets a WebClient User-Agent header of PowerShell then pipes a DownloadString response straight into iex, the delivery command for the new PHP-based Interlock RAT variant. Adversaries use this fake-captcha clipboard lure to run a hidden bypass PowerShell that pulls and executes remote code, so a WebClient header set to PowerShell combined with DownloadString and iex is a high-confidence execution signal.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

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Malicious Powerfun Reverse Shell Script via Script Block (via ps_script)

Suspicious PowerShell Stager Download of Spf Script by Seedworm

Windows curl.exe SOCKS Proxy and .onion Command-Line Execution

Malicious Interlock RAT FileFix Download-Cradle via PowerShell WebClient with PowerShell User-Agent (via ps_script)

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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