Suspicious NTLM Authentication on the Printer Spooler Service

Severity: high
Author: Elastic (idea), Tobias Michalski (Nextron Systems)
Source: upstream

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

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

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

Stage 2: `all of selection_cli`

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

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.

Field	Kind	Values
`CommandLine`	match	`/print/pipe/` `C:\windows\system32\davclnt.dll,DavSetCookie` corpus 3 (sigma 3) `http` corpus 31 (sigma 31) `spoolss` `srvsvc`
`Image`	ends_with	`\rundll32.exe` corpus 76 (sigma 76)
`OriginalFileName`	eq	`RUNDLL32.EXE` corpus 28 (sigma 25, splunk 3)