Malicious AMSI and ETW Patching via PowerShell Script

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects PowerShell script content that references AmsiScanBuffer or EtwEventWrite in order to patch the Antimalware Scan Interface and Event Tracing for Windows, an in-memory evasion step UAT-11795 performs before injecting the Starland RAT as reported by Cisco Talos. Tampering with these logging and scanning interfaces blinds defenses. Detecting the patch strings exposes active defense evasion in the loader.

Reporting behind it

Related detections9 linkedT1685 — drag to rearrange

Malicious UAC Disable via EnableLUA Registry Modification (via registry_set)

Malicious PowMix AMSI Bypass via amsiInitFailed

Suspicious ThrottleStop Driver Abuse for Defense Evasion in Ransomware Attacks

Malicious Disabling of Microsoft Defender Real-Time Protection via SystemSettingsAdminFlows by DeadLock Ransomware

Suspicious Security Software Uninstallation via WMIC Product Call Uninstall (Chaos Ransomware)

Suspicious Security Product Uninstall via wmic product call uninstall

Suspicious Windows Defender Exclusion Added for ProgramData (via process_creation)

Windows Firewall Disabled via netsh advfirewall

Malicious Known Vulnerable Driver Load for BYOVD Attack

Malicious AMSI and ETW Patching via PowerShell Script

Pivot detection · T1685 · 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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