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Detection rules › Sigma

Decode Base64 Encoded Text -MacOs

Status
test
Severity
low
Log source
category process_creation, product macos
Author
Daniil Yugoslavskiy, oscd.community
Source
github.com/SigmaHQ/sigma

Detects usage of base64 utility to decode arbitrary base64-encoded text

Known false positives

  • Legitimate activities

MITRE ATT&CK coverage

TacticTechniques
Stealth

Telemetry coverage

PlatformRecord / event type
macOSESF event exec (NOTIFY): Fires after execve(2) or posix_spawn(2) succeeds, delivering a post-fact record of the new process.

Rule body

title: Decode Base64 Encoded Text -MacOs
id: 719c22d7-c11a-4f2c-93a6-2cfdd5412f68
status: test
description: Detects usage of base64 utility to decode arbitrary base64-encoded text
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1027/T1027.md
author: Daniil Yugoslavskiy, oscd.community
date: 2020-10-19
modified: 2022-11-26
tags:
    - attack.stealth
    - attack.t1027
logsource:
    category: process_creation
    product: macos
detection:
    selection:
        Image: '/usr/bin/base64'
        CommandLine|contains: '-d'
    condition: selection
falsepositives:
    - Legitimate activities
level: low

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image: '/usr/bin/base64'
    CommandLine|contains: '-d'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
CommandLinematch
  • -d
field:"CommandLine" kind:match value:"-d"
Imageeq
  • /usr/bin/base64
field:"Image" kind:eq value:"/usr/bin/base64"