Malicious In-Memory Payload Execution via PowerShell DownloadString (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 downloading a script from a remote host and immediately executing it in memory using DownloadString together with Invoke-Expression, a fileless technique used by a ransomware actor after ColdFusion exploitation to run Cobalt Strike beacons and reverse shells. Combining a web download with immediate expression evaluation is a common malicious loader pattern.

Reporting behind it

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Malicious In-Memory Payload Execution via PowerShell DownloadString (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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