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Elastic Docs ›Elastic Security Solution [8.0] ›Detections and alerts ›Prebuilt rule reference

PowerShell Suspicious Payload Encoded and Compressed

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PowerShell Suspicious Payload Encoded and Compressed

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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.

Rule type: query

Rule indices:

  • winlogbeat-*
  • logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Defense Evasion

Version: 1

Added (Elastic Stack release): 8.0.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Legitimate PowerShell Scripts which makes use of compression and encoding

Rule query

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event.category:process 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 )

Threat mapping

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Framework: MITRE ATT&CKTM

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