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Detection rules › Sigma

CVE-2023-23397 Exploitation Attempt

Status
test
Severity
critical
Log source
product windows, service security
Author
Robert Lee @quantum_cookie
Source
github.com/SigmaHQ/sigma

Detects outlook initiating connection to a WebDAV or SMB share, which could be a sign of CVE-2023-23397 exploitation.

MITRE ATT&CK coverage

TacticTechniques
Initial AccessNo specific technique
Credential AccessNo specific technique

Event coverage

ProviderEventTitle
Security-AuditingEvent ID 4656A handle to an object was requested.
Security-AuditingEvent ID 4663An attempt was made to access an object.

Rule body yaml

title: CVE-2023-23397 Exploitation Attempt
id: 73c59189-6a6d-4b9f-a748-8f6f9bbed75c
status: test
description: Detects outlook initiating connection to a WebDAV or SMB share, which could be a sign of CVE-2023-23397 exploitation.
author: Robert Lee @quantum_cookie
date: 2023-03-16
modified: 2023-03-22
references:
    - https://www.trustedsec.com/blog/critical-outlook-vulnerability-in-depth-technical-analysis-and-recommendations-cve-2023-23397/
tags:
    - attack.credential-access
    - attack.initial-access
    - cve.2023-23397
    - detection.emerging-threats
logsource:
    service: security
    product: windows
    definition: 'Requirements: SACLs must be enabled for "Query Value" on the registry keys used in this rule'
detection:
    selection:
        EventID:
            - 4656
            - 4663
        ProcessName|endswith: '\OUTLOOK.EXE'
        # Example: \REGISTRY\MACHINE\SYSTEM\CurrentControlSet001\Services\WebClient\NetworkProvider
        ObjectName|contains|all:
            - '\REGISTRY\MACHINE\SYSTEM'
            - 'Services\'
        ObjectName|endswith:
            - 'WebClient\NetworkProvider'
            - 'LanmanWorkstation\NetworkProvider'
        AccessList|contains: '%%4416' # "Query key value"
    condition: selection
falsepositives:
    - Searchprotocolhost.exe likes to query these registry keys. To avoid false postives, it's better to filter out those events before they reach the SIEM
level: critical

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    EventID:
        - 4656
        - 4663
    ProcessName|endswith: '\OUTLOOK.EXE'
    ObjectName|contains|all:
        - '\REGISTRY\MACHINE\SYSTEM'
        - 'Services\'
    ObjectName|endswith:
        - 'WebClient\NetworkProvider'
        - 'LanmanWorkstation\NetworkProvider'
    AccessList|contains: '%%4416'

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
AccessListmatch
  • %%4416
ObjectNameends_with
  • LanmanWorkstation\NetworkProvider
  • WebClient\NetworkProvider
ObjectNamematch
  • Services\
  • \REGISTRY\MACHINE\SYSTEM corpus 2 (sigma 2)
ProcessNameends_with
  • \OUTLOOK.EXE