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Detection rules › Sigma

ProxyLogon Reset Virtual Directories Based On IIS Log

Status
test
Severity
critical
Log source
category webserver
Author
frack113
Source
github.com/SigmaHQ/sigma

When exploiting this vulnerability with CVE-2021-26858, an SSRF attack is used to manipulate virtual directories

Known false positives

  • Unlikely

MITRE ATT&CK coverage

TacticTechniques
Initial Access

Rule body

title: ProxyLogon Reset Virtual Directories Based On IIS Log
id: effee1f6-a932-4297-a81f-acb44064fa3a
status: test
description: When exploiting this vulnerability with CVE-2021-26858, an SSRF attack is used to manipulate virtual directories
references:
    - https://bi-zone.medium.com/hunting-down-ms-exchange-attacks-part-1-proxylogon-cve-2021-26855-26858-27065-26857-6e885c5f197c
author: frack113
date: 2021-08-10
modified: 2023-05-08
tags:
    - cve.2021-26858
    - detection.emerging-threats
    - attack.initial-access
    - attack.t1190
logsource:
    category: webserver
    definition: 'Requirements: The POST request body data must be collected in order to make use of this detection'
detection:
    selection:
        cs-method: 'POST'
        sc-status: 200
        cs-uri-stem: '/ecp/DDI/DDIService.svc/SetObject'
        cs-uri-query|contains|all:
            - 'schema=Reset'
            - 'VirtualDirectory'
        cs-username|endswith: '$'
    keywords:
        '|all':
            - 'POST'
            - 200
            - '/ecp/DDI/DDIService.svc/SetObject'
            - 'schema=Reset'
            - 'VirtualDirectory'
            - '$'
    condition: selection or keywords
falsepositives:
    - Unlikely
level: critical

Stages and Predicates

Stage 0: condition

selection or keywords

Stage 1: selection

selection:
    cs-method: 'POST'
    sc-status: 200
    cs-uri-stem: '/ecp/DDI/DDIService.svc/SetObject'
    cs-uri-query|contains|all:
        - 'schema=Reset'
        - 'VirtualDirectory'
    cs-username|endswith: '$'

Stage 2: keywords

keywords:
    '|all':
        - 'POST'
        - 200
        - '/ecp/DDI/DDIService.svc/SetObject'
        - 'schema=Reset'
        - 'VirtualDirectory'
        - '$'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
cs-methodeq
  • POST
field:"cs-method" kind:eq value:"POST"
cs-uri-querymatch
  • VirtualDirectory
  • schema=Reset
field:"cs-uri-query" kind:match
cs-uri-stemeq
  • /ecp/DDI/DDIService.svc/SetObject
field:"cs-uri-stem" kind:eq value:"/ecp/DDI/DDIService.svc/SetObject"
cs-usernameends_with
  • $
field:"cs-username" kind:ends_with value:"$"
sc-statuseq
  • 200
field:"sc-status" kind:eq value:"200"