Elastic Security Detection Rules

PowerShell Suspicious Payload Encoded and Compressed

Last updated 9 months ago on 2025-03-20
Created 4 years ago on 2021-10-19

About

Identifies the use of .NET functionality for decompression and base64 decoding combined in PowerShell scripts, which malware and security tools heavily use to deobfuscate payloads and load them directly in memory to bypass defenses.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Defense EvasionData Source: PowerShell LogsLanguage: kuery
Severity
high
Risk Score
73
MITRE ATT&CK™

Defense Evasion (TA0005)(external, opens in a new tab or window)

↳ Obfuscated Files or Information (T1027)(external, opens in a new tab or window)

↳ Deobfuscate/Decode Files or Information (T1140)(external, opens in a new tab or window)

Execution (TA0002)(external, opens in a new tab or window)

↳ Command and Scripting Interpreter (T1059)(external, opens in a new tab or window)

False Positive Examples
Legitimate PowerShell Scripts which makes use of compression and encoding.
License
Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type
Query (Kibana Query Language)
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
winlogbeat-*logs-windows.powershell*
Related Integrations

windows(external, opens in a new tab or window)

Query
text code block:
event.category:process and host.os.type:windows and
  powershell.file.script_block_text : (
    (
      "System.IO.Compression.DeflateStream" or
      "System.IO.Compression.GzipStream" or
      "IO.Compression.DeflateStream" or
      "IO.Compression.GzipStream"
    ) and
    FromBase64String
  ) and
  not user.id : "S-1-5-18"

Install detection rules in Elastic Security

Detect PowerShell Suspicious Payload Encoded and Compressed in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).