Windows Rundll32 Calls DavSetCookie for NTLM Coercion via Spoolss/Srvsvc

title: Windows Rundll32 Calls DavSetCookie for NTLM Coercion via Spoolss/Srvsvc
id: a5fd97ff-9c4c-47a9-bf7d-ba2a0f07d597
status: test
description: This rule flags process execution of rundll32.exe invoking davclnt.dll,DavSetCookie with HTTP-related parameters tied to spoolss and srvsvc named-pipe targeting. This behavior can be used to coerce an NTLM authentication attempt through the Printer Spooler/SMB print service pathway, which may enable credential relay and privilege escalation. It relies on process creation telemetry, matching rundll32 image details and specific command-line substrings used in the invocation.
references:
  - https://twitter.com/med0x2e/status/1520402518685200384
  - https://github.com/elastic/detection-rules/blob/dd224fb3f81d0b4bf8593c5f02a029d647ba2b2d/rules/windows/credential_access_relay_ntlm_auth_via_http_spoolss.toml
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_rundll32_ntlmrelay.yml
author: Elastic (idea), Tobias Michalski (Nextron Systems), Huntrule Team
date: 2022-05-04
modified: 2023-02-09
tags:
  - attack.privilege-escalation
  - attack.credential-access
  - attack.t1212
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith: \rundll32.exe
    - OriginalFileName: RUNDLL32.EXE
  selection_cli:
    CommandLine|contains|all:
      - C:\windows\system32\davclnt.dll,DavSetCookie
      - http
    CommandLine|contains:
      - spoolss
      - srvsvc
      - /print/pipe/
  condition: all of selection_*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: bb76d96b-821c-47cf-944b-7ce377864492
    type: derived