Network Connection Initiated By PowerShell Process

SIGMA detection rule by Florian Roth (Nextron Systems) · NOASSERTION

Detects a network connection that was initiated from a PowerShell process. Often times malicious powershell scripts download additional payloads or communicate back to command and control channels via uncommon ports or IPs. Use this rule as a basis for hunting for anomalies.

title: Network Connection Initiated By PowerShell Process
id: 1f21ec3f-810d-4b0e-8045-322202e22b4b
status: test
description: |
    Detects a network connection that was initiated from a PowerShell process.
    Often times malicious powershell scripts download additional payloads or communicate back to command and control channels via uncommon ports or IPs.
    Use this rule as a basis for hunting for anomalies.
references:
    - https://www.youtube.com/watch?v=DLtJTxMWZ2o
author: Florian Roth (Nextron Systems)
date: 2017-03-13
modified: 2024-03-13
tags:
    - attack.execution
    - attack.t1059.001
    - detection.threat-hunting
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Image|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        Initiated: 'true'
    filter_main_local_ip:
        DestinationIp|cidr:
            - '127.0.0.0/8'
            - '10.0.0.0/8'
            - '169.254.0.0/16'  # link-local address
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '::1/128'  # IPv6 loopback
            - 'fe80::/10'  # IPv6 link-local addresses
            - 'fc00::/7'  # IPv6 private addresses
        User|contains: # covers many language settings
            - 'AUTHORI'
            - 'AUTORI'
    filter_main_msrange:
        DestinationIp|cidr:
            - '20.184.0.0/13'
            - '51.103.210.0/23'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Administrative scripts
    - Microsoft IP range
    - Additional filters are required. Adjust to your environment (e.g. extend filters with company's ip range')
level: low

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

2aae3bde-59c1-434c-9a05-16ef6617c2a8

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

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