Malicious PowerShell Download Cradle With DownloadString

ATT&CK techniques

Execution

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

What it detects

This rule detects a hidden PowerShell process invoking a WebClient DownloadString cradle piped into Invoke-Expression. In the WithSecure Initial Access Lab 1 the macro launches powershell with Sta Nop and Hidden window flags to fetch and execute a remote script in memory. Attackers use this fileless download cradle to run second stage code without touching disk.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

Suspicious PowerShell Encoded Command Execution

Suspicious PowerShell Hidden Download Cradle via IEX

Suspicious PowerShell IEX Execution of documentLoger Payload via CharmingCypress

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

Malicious PowerShell Executing Script From Public Directory via WScript

Suspicious PowerShell Executing Payload From Roaming AppData via Command Line (via process_creation)

Suspicious PowerShell Spawning mshta for Malware Execution (via process_creation)

Malicious SolarWinds BusinessLayerHost Spawning Suspicious Child Process (SUNBURST) (via process_creation)

Suspicious word_update.exe Spawning Command Shell in Remcos Chain (via process_creation)

Malicious PowerShell Download Cradle With DownloadString

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.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →