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Detection rules › Sigma

Potential Startup Shortcut Persistence Via PowerShell.EXE

Status
test
Severity
high
Log source
product windows, category file_event
Author
Christopher Peacock '@securepeacock', SCYTHE
Source
github.com/SigmaHQ/sigma

Detects PowerShell writing startup shortcuts. This procedure was highlighted in Red Canary Intel Insights Oct. 2021, "We frequently observe adversaries using PowerShell to write malicious .lnk files into the startup directory to establish persistence. Accordingly, this detection opportunity is likely to identify persistence mechanisms in multiple threats. In the context of Yellow Cockatoo, this persistence mechanism eventually launches the command-line script that leads to the installation of a malicious DLL"

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1547.001 Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder
Privilege EscalationT1547.001 Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

title: Potential Startup Shortcut Persistence Via PowerShell.EXE
id: 92fa78e7-4d39-45f1-91a3-8b23f3f1088d
status: test
description: |
    Detects PowerShell writing startup shortcuts.
    This procedure was highlighted in Red Canary Intel Insights Oct. 2021, "We frequently observe adversaries using PowerShell to write malicious .lnk files into the startup directory to establish persistence.
    Accordingly, this detection opportunity is likely to identify persistence mechanisms in multiple threats.
    In the context of Yellow Cockatoo, this persistence mechanism eventually launches the command-line script that leads to the installation of a malicious DLL"
references:
    - https://redcanary.com/blog/intelligence-insights-october-2021/
    - https://github.com/redcanaryco/atomic-red-team/blob/36d49de4c8b00bf36054294b4a1fcbab3917d7c5/atomics/T1547.001/T1547.001.md#atomic-test-7---add-executable-shortcut-link-to-user-startup-folder
author: Christopher Peacock '@securepeacock', SCYTHE
date: 2021-10-24
modified: 2023-02-23
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1547.001
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith:
            - '\powershell.exe'
            - '\pwsh.exe'
        TargetFilename|contains: '\start menu\programs\startup\'
        TargetFilename|endswith: '.lnk'
    condition: selection
falsepositives:
    - Depending on your environment accepted applications may leverage this at times. It is recommended to search for anomalies inidicative of malware.
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    TargetFilename|contains: '\start menu\programs\startup\'
    TargetFilename|endswith: '.lnk'

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
Imageends_with
  • \powershell.exe corpus 182 (sigma 182)
  • \pwsh.exe corpus 168 (sigma 168)
TargetFilenameends_with
  • .lnk corpus 6 (sigma 6)
TargetFilenamematch
  • \start menu\programs\startup\ corpus 5 (sigma 5)