bXOR Operator Usage In PowerShell Command Line - PowerShell Classic

SIGMA detection rule by Teymur Kheirkhabarov, Harish Segar · NOASSERTION

Detects powershell execution with that make use of to the bxor (Bitwise XOR). Attackers might use as an alternative obfuscation method to Base64 encoded commands. Investigate the CommandLine and process tree to determine if the activity is malicious.

title: bXOR Operator Usage In PowerShell Command Line - PowerShell Classic
id: 812837bb-b17f-45e9-8bd0-0ec35d2e3bd6
status: test
description: |
    Detects powershell execution with that make use of to the bxor (Bitwise XOR).
    Attackers might use as an alternative obfuscation method to Base64 encoded commands.
    Investigate the CommandLine and process tree to determine if the activity is malicious.
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=46
    - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_arithmetic_operators?view=powershell-5.1
author: Teymur Kheirkhabarov, Harish Segar
date: 2020-06-29
modified: 2024-12-11
tags:
    - attack.execution
    - attack.t1059.001
    - detection.threat-hunting
logsource:
    product: windows
    category: ps_classic_start
detection:
    selection:
        Data|contains|all:
            - 'HostName=ConsoleHost'
            - ' -bxor '
    condition: selection
falsepositives:
    - Unknown
level: low

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

179d34c4-1543-412c-92cc-0a8b7c012c06

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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