Potential Azure Browser SSO Abuse — Sigma Rule

Rule metadata and linked tags

Author: Den Iuzvyk. Source status: test; severity: low. Source dates: 2020-07-15 / 2023-04-18.

{
  "category": "image_load",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8a6c33b31b57d35958e06a11634e4be1f1695e85e2019d98116a5c21cd27e550

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Potential Azure Browser SSO Abuse
id: 50f852e6-af22-4c78-9ede-42ef36aa3453
status: test
description: |
    Detects abusing Azure Browser SSO by requesting OAuth 2.0 refresh tokens for an Azure-AD-authenticated Windows user (i.e. the machine is joined to Azure AD and a user logs in with their Azure AD account) wanting to perform SSO authentication in the browser.
    An attacker can use this to authenticate to Azure AD in a browser as that user.
references:
    - https://posts.specterops.io/requesting-azure-ad-request-tokens-on-azure-ad-joined-machines-for-browser-sso-2b0409caad30
author: Den Iuzvyk
date: 2020-07-15
modified: 2023-04-18
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
    - attack.stealth
    - attack.t1574.001
logsource:
    category: image_load
    product: windows
detection:
    selection:
        ImageLoaded: 'C:\Windows\System32\MicrosoftAccountTokenProvider.dll'
    filter_main_bgtaskhost:
        Image|startswith:
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
        Image|endswith: '\BackgroundTaskHost.exe'
        # CommandLine|contains: '-ServerNameBackgroundTaskHost.WebAccountProvider'
    filter_optional_devenv:
        Image|startswith:
            - 'C:\Program Files\Microsoft Visual Studio\'
            - 'C:\Program Files (x86)\Microsoft Visual Studio\'
        Image|endswith: '\IDE\devenv.exe'
    filter_optional_ie:
        Image:
            - 'C:\Program Files (x86)\Internet Explorer\iexplore.exe'
            - 'C:\Program Files\Internet Explorer\iexplore.exe'
    filter_optional_edge_1:
        - Image|startswith: 'C:\Program Files (x86)\Microsoft\EdgeWebView\Application\'
        - Image|endswith: '\WindowsApps\MicrosoftEdge.exe'
        - Image:
              - 'C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
              - 'C:\Program Files\Microsoft\Edge\Application\msedge.exe'
    filter_optional_edge_2:
        Image|startswith:
            - 'C:\Program Files (x86)\Microsoft\EdgeCore\'
            - 'C:\Program Files\Microsoft\EdgeCore\'
        Image|endswith:
            - '\msedge.exe'
            - '\msedgewebview2.exe'
    filter_optional_onedrive:
        Image|endswith: '\AppData\Local\Microsoft\OneDrive\OneDrive.exe'
    filter_optional_null:
        Image: null
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - False positives are expected since this rules is only looking for the DLL load event. This rule is better used in correlation with related activity
level: low

Original YAML and metadata in JSON

False positives

• False positives are expected since this rules is only looking for the DLL load event. This rule is better used in correlation with related activity

Source references

• https://posts.specterops.io/requesting-azure-ad-request-tokens-on-azure-ad-joined-machines-for-browser-sso-2b0409caad30