Uncommon Extension Shim Database Installation Via Sdbinst.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects installation of a potentially suspicious new shim with an uncommon extension using sdbinst.exe. Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by application shims

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1546.011` Event Triggered Execution: Application Shimming
Privilege Escalation	`T1546.011` Event Triggered Execution: Application Shimming

Telemetry coverage

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

Rule body

title: Uncommon Extension Shim Database Installation Via Sdbinst.EXE
id: 18ee686c-38a3-4f65-9f44-48a077141f42
related:
    - id: 517490a7-115a-48c6-8862-1a481504d5a8
      type: derived
status: test
description: |
    Detects installation of a potentially suspicious new shim with an uncommon extension using sdbinst.exe.
    Adversaries may establish persistence and/or elevate privileges by executing malicious content triggered by application shims
references:
    - https://www.fireeye.com/blog/threat-research/2017/05/fin7-shim-databases-persistence.html
    - https://github.com/nasbench/Misc-Research/blob/8ee690e43a379cbce8c9d61107442c36bd9be3d3/Other/Undocumented-Flags-Sdbinst.md
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-08-01
modified: 2024-01-10
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.t1546.011
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\sdbinst.exe'
        - OriginalFileName: 'sdbinst.exe'
    filter_main_legit_ext:
        CommandLine|contains: '.sdb'
    filter_main_legit_extensions:
        # ParentImage|endswith: ':\Windows\System32\svchost.exe'
        - CommandLine|endswith:
              - ' -c'
              - ' -f'
              - ' -mm'
              - ' -t'
        - CommandLine|contains: ' -m -bg'
    filter_main_null:
        CommandLine: null
    filter_main_empty:
        CommandLine: ''
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    - Image|endswith: '\sdbinst.exe'
    - OriginalFileName: 'sdbinst.exe'

Stage 2: `not filter_main_*`

filter_main_legit_ext:
    CommandLine|contains: '.sdb'
filter_main_legit_extensions:
    - CommandLine|endswith:
          - ' -c'
          - ' -f'
          - ' -mm'
          - ' -t'
    - CommandLine|contains: ' -m -bg'
filter_main_null:
    CommandLine: null
filter_main_empty:
    CommandLine: ''

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`CommandLine`	ends_with	`-c`	`excludes:CommandLine` `field:"CommandLine" value:" -c"`
`CommandLine`	ends_with	`-f`	`excludes:CommandLine` `field:"CommandLine" value:" -f"`
`CommandLine`	ends_with	`-mm`	`excludes:CommandLine` `field:"CommandLine" value:" -mm"`
`CommandLine`	ends_with	`-t`	`excludes:CommandLine` `field:"CommandLine" value:" -t"`
`CommandLine`	is_null	(no value, null check)	`excludes:CommandLine`
`CommandLine`	match	`-m -bg`	`excludes:CommandLine` `field:"CommandLine" value:" -m -bg"`
`CommandLine`	match	`.sdb`	`excludes:CommandLine` `field:"CommandLine" value:".sdb"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\sdbinst.exe` corpus 2 (sigma 2)	`field:"Image" kind:ends_with value:"\sdbinst.exe"`
`OriginalFileName`	eq	`sdbinst.exe` corpus 2 (sigma 2)	`field:"OriginalFileName" kind:eq value:"sdbinst.exe"`