Suspicious NTLM Authentication on the Printer Spooler Service

Status: test
Severity: high
Log source: category process_creation, product windows
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

Tactic	Techniques
Credential Access	`T1212` Exploitation for Credential Access

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`/print/pipe/` `C:\windows\system32\davclnt.dll,DavSetCookie` corpus 3 (sigma 3) `http` corpus 52 (sigma 34, elastic 15, chronicle 2, splunk 1) `spoolss` `srvsvc`	`field:"CommandLine" kind:match`
`Image`	ends_with	`\rundll32.exe` corpus 94 (sigma 94)	`field:"Image" kind:ends_with value:"\rundll32.exe"`
`OriginalFileName`	eq	`RUNDLL32.EXE` corpus 78 (sigma 35, elastic 22, splunk 21)	`field:"OriginalFileName" kind:eq value:"RUNDLL32.EXE"`

Suspicious NTLM Authentication on the Printer Spooler Service

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_cli

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`