1200KM / sigma-rule
Suspicious FromBase64String Usage On Gzip Archive - Process Creation — Sigma Rule
Sigma rule d75d6b6b-adb9-48f7-824b-ac2e786efe1f. Suspicious FromBase64String Usage On Gzip Archive - Process Creation — Sigma Rule. Detects attempts of decoding a base64 Gzip archive via PowerShell. This technique is often used as a method to load malicious content into memory afterward.
Rule metadata and linked tags
Author: frack113. Source status: test; severity: medium. Source dates: 2022-12-23 / not supplied.
{
"product": "windows",
"category": "process_creation"
}Pinned original Sigma rule · Detection Rule License 1.1
Source SHA-256: 9a09d9e99a77b2a18321f6dcc3eb8d1c950d96f59d0ea41016523fafc3ef9c41
Detection logic
Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.
title: Suspicious FromBase64String Usage On Gzip Archive - Process Creation
id: d75d6b6b-adb9-48f7-824b-ac2e786efe1f
related:
- id: df69cb1d-b891-4cd9-90c7-d617d90100ce
type: similar
status: test
description: Detects attempts of decoding a base64 Gzip archive via PowerShell. This technique is often used as a method to load malicious content into memory afterward.
references:
- https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=43
author: frack113
date: 2022-12-23
tags:
- attack.command-and-control
- attack.t1132.001
logsource:
product: windows
category: process_creation
detection:
selection:
CommandLine|contains|all:
- 'FromBase64String'
- 'MemoryStream'
- 'H4sI'
condition: selection
falsepositives:
- Legitimate administrative script
level: medium
False positives
- Legitimate administrative script
Source references
Connected ecosystem references
Exact source-tagged techniques
Telemetry review
Read the original logsource above, then inspect the linked detection workspaces for technique-level sensor context. No per-rule telemetry equivalence is inferred.
Pinned research references. No browser attack runner, live simulation result or validated detector is asserted. Source mappings and validation limits are preserved. ATT&CK / Atomic provenance · Detection provenance.