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

Event coverage

Provider	Event	Title
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 yaml

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

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

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

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

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

LSASS Access From Non System Account

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_*`

Stage 3: `not filter_optional_steam`

Exclusions

Indicators

Keyboard shortcuts

Search operators

LSASS Access From Non System Account

MITRE ATT&CK coverage

Event coverage

Rule body yaml

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`