LSASS Access From Non System Account

Status: test
Severity: medium
Log source: product windows, service security
Author: Roberto Rodriguez @Cyb3rWard0g
Source: github.com/SigmaHQ/sigma

Detects potential mimikatz-like tools accessing LSASS from non system account

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1003.001` OS Credential Dumping: LSASS Memory

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4656: A handle to an object was requested.
Security-Auditing	Event ID 4663: An attempt was made to access an object.

Rule body

title: LSASS Access From Non System Account
id: 962fe167-e48d-4fd6-9974-11e5b9a5d6d1
status: test
description: Detects potential mimikatz-like tools accessing LSASS from non system account
references:
    - https://threathunterplaybook.com/hunts/windows/170105-LSASSMemoryReadAccess/notebook.html
author: Roberto Rodriguez @Cyb3rWard0g
date: 2019-06-20
modified: 2023-12-11
tags:
    - attack.credential-access
    - attack.t1003.001
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID:
            - 4663
            - 4656
        AccessMask:
            - '0x100000'
            - '0x1010'    # car.2019-04-004
            - '0x1400'
            - '0x1410'    # car.2019-04-004
            - '0x1418'    # car.2019-04-004
            - '0x1438'    # car.2019-04-004
            - '0x143a'    # car.2019-04-004
            - '0x1f0fff'
            - '0x1f1fff'
            - '0x1f2fff'
            - '0x1f3fff'
            - '0x40'
            - '143a'    # car.2019-04-004
            - '1f0fff'
            - '1f1fff'
            - '1f2fff'
            - '1f3fff'
            # - '0x1000'  # minimum access requirements to query basic info from service
        ObjectType: 'Process'
        ObjectName|endswith: '\lsass.exe'
    filter_main_service_account:
        SubjectUserName|endswith: '$'
    filter_main_generic:
        ProcessName|contains:
            # Legitimate AV and EDR solutions
            - ':\Program Files\'
            - ':\Program Files (x86)\'
    filter_main_wmiprvse:
        ProcessName: 'C:\Windows\System32\wbem\WmiPrvSE.exe'
        AccessMask: '0x1410'
    filter_optional_steam:
        ProcessName|contains: '\SteamLibrary\steamapps\'
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    EventID:
        - 4663
        - 4656
    AccessMask:
        - '0x100000'
        - '0x1010'
        - '0x1400'
        - '0x1410'
        - '0x1418'
        - '0x1438'
        - '0x143a'
        - '0x1f0fff'
        - '0x1f1fff'
        - '0x1f2fff'
        - '0x1f3fff'
        - '0x40'
        - '143a'
        - '1f0fff'
        - '1f1fff'
        - '1f2fff'
        - '1f3fff'
    ObjectType: 'Process'
    ObjectName|endswith: '\lsass.exe'

Stage 2: `not filter_main_*`

filter_main_service_account:
    SubjectUserName|endswith: '$'
filter_main_generic:
    ProcessName|contains:
        - ':\Program Files\'
        - ':\Program Files (x86)\'
filter_main_wmiprvse:
    ProcessName: 'C:\Windows\System32\wbem\WmiPrvSE.exe'
    AccessMask: '0x1410'

Stage 3: `not filter_optional_steam`

filter_optional_steam:
    ProcessName|contains: '\SteamLibrary\steamapps\'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`AccessMask`	eq	`0x1410`	`excludes:AccessMask` `field:"AccessMask" value:"0x1410"`
`ProcessName`	eq	`C:\Windows\System32\wbem\WmiPrvSE.exe`	`excludes:ProcessName` `field:"ProcessName" value:"C:\Windows\System32\wbem\WmiPrvSE.exe"`
`ProcessName`	match	`:\Program Files (x86)\`	`excludes:ProcessName` `field:"ProcessName" value:":\Program Files (x86)\"`
`ProcessName`	match	`:\Program Files\`	`excludes:ProcessName` `field:"ProcessName" value:":\Program Files\"`
`SubjectUserName`	ends_with	`$`	`excludes:SubjectUserName` `field:"SubjectUserName" value:"$"`
`ProcessName`	match	`\SteamLibrary\steamapps\`	`excludes:ProcessName` `field:"ProcessName" value:"\SteamLibrary\steamapps\"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`AccessMask`	eq	`0x100000` `0x1010` `0x1400` `0x1410` `0x1418` `0x1438` `0x143a` `0x1f0fff` `0x1f1fff` `0x1f2fff` `0x1f3fff` `0x40` `143a` `1f0fff` `1f1fff` `1f2fff` `1f3fff`	`field:"AccessMask" kind:eq`
`ObjectName`	ends_with	`\lsass.exe` corpus 4 (sigma 4)	`field:"ObjectName" kind:ends_with value:"\lsass.exe"`
`ObjectType`	eq	`Process` corpus 4 (sigma 3, elastic 1)	`field:"ObjectType" kind:eq value:"Process"`

LSASS Access From Non System Account

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_*

Stage 3: not filter_optional_steam

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_optional_steam`