detection.wiki

Detection rules › Sigma

Base64 Encoded PowerShell Command Detected

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects usage of the "FromBase64String" function in the commandline which is used to decode a base64 encoded string

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1059.001 Command and Scripting Interpreter: PowerShell
StealthT1027 Obfuscated Files or Information, T1140 Deobfuscate/Decode Files or Information

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

title: Base64 Encoded PowerShell Command Detected
id: e32d4572-9826-4738-b651-95fa63747e8a
status: test
description: Detects usage of the "FromBase64String" function in the commandline which is used to decode a base64 encoded string
references:
    - https://gist.github.com/Neo23x0/6af876ee72b51676c82a2db8d2cd3639
author: Florian Roth (Nextron Systems)
date: 2020-01-29
modified: 2023-01-26
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1140
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: '::FromBase64String('
    condition: selection
falsepositives:
    - Administrative script libraries
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    CommandLine|contains: '::FromBase64String('

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • ::FromBase64String( corpus 2 (sigma 1, chronicle 1)