Suspicious PowerShell WebClient UploadString Network Beacon

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 PowerShell using a Net.WebClient object with the UploadString method to send data to a remote server. The GoPix banking trojan used LNK-launched PowerShell to POST victim data and receive tasking via WebClient UploadString as documented by Kaspersky. The uploading variant of WebClient is uncommon in benign scripting and indicates outbound command-and-control or data exfiltration.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange

Suspicious PowerShell Web Request to oastify Out-of-Band Domain

Suspicious PowerShell Spawned by Web Browser

Suspicious PowerShell Interaction with ProgramData SysInt Log via Process Creation

Suspicious PowerShell Invoke-WebRequest Piped to Invoke-Expression via FakeBat Loader

Suspicious PowerShell COM-Based Script Execution and HTTP Retrieval (via ps_script)

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

Suspicious PowerShell Decoding Base64 Payload Stored in Registry

Suspicious PowerShell WebClient UploadString Network Beacon

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 →