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Detection rules › Sigma

Suspicious NTLM Authentication on the Printer Spooler Service

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Elastic (idea), Tobias Michalski (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects a privilege elevation attempt by coercing NTLM authentication on the Printer Spooler service

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1212 Exploitation for Credential Access

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Suspicious NTLM Authentication on the Printer Spooler Service
id: bb76d96b-821c-47cf-944b-7ce377864492
status: test
description: Detects a privilege elevation attempt by coercing NTLM authentication on the Printer Spooler service
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
author: Elastic (idea), Tobias Michalski (Nextron Systems)
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

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_img

selection_img:
    - Image|endswith: '\rundll32.exe'
    - OriginalFileName: 'RUNDLL32.EXE'

Stage 2: selection_cli

selection_cli:
    CommandLine|contains|all:
        - 'C:\windows\system32\davclnt.dll,DavSetCookie'
        - 'http'
    CommandLine|contains:
        - 'spoolss'
        - 'srvsvc'
        - '/print/pipe/'

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
CommandLinematch
  • /print/pipe/
  • C:\windows\system32\davclnt.dll,DavSetCookie corpus 3 (sigma 3)
  • http corpus 39 (sigma 34, elastic 2, chronicle 2, splunk 1)
  • spoolss
  • srvsvc
Imageends_with
  • \rundll32.exe corpus 95 (sigma 95)
OriginalFileNameeq
  • RUNDLL32.EXE corpus 62 (sigma 35, splunk 21, elastic 6)