huntrule

PowerShell Net.WebClient DownloadFile/DownloadString Usage (Classic)

Flags PowerShell Classic commands using Net.WebClient to download content via DownloadFile or DownloadString.

FreeReviewedSigma · Low · v2
Product
windows
Category
ps_classic_start
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2017-03-05
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution → C2

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies PowerShell classic execution that uses the Net.WebClient class to download content via the .DownloadFile() or .DownloadString() methods. Downloading external content is a common step attackers use to obtain additional payloads or stage follow-on activity. Telemetry relies on PowerShell start logs capturing the script content that includes Net.WebClient and the specific download method calls.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange
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)
Suspicious node.exe Execution Spawned by PowerShell
Suspicious PowerShell Download Cradle via IEX and DownloadString (via process_creation)
Suspicious PowerShell Download to Temp and In-Memory Execution via IEX (via process_creation)
Suspicious ClickFix cv.bat Staging in Temp via PowerShell (via process_creation)
PowerShell Net.WebClient DownloadFile/DownloadString Usage (Classic)
Pivot detection · T1059.001 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

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