CrackMaxpExec share permission enumeration

Status: experimental
Severity: medium
Time window: 15m
Log source: product windows, service security
Author: mdecrevoisier
Source: github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where an attacker would perform share permission enumeration using CrackMaxExec SMBmodule.

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 5145	A network share object was checked to see whether client can be granted desired access.

Rule body yaml

title: CrackMaxpExec share permission enumeration
description: Detects scenarios where an attacker would perform share permission enumeration using CrackMaxExec SMBmodule.
correlation: correlate TargetLogonId from ID 4624 with SubjectLogonId from ID 5145 to identify the source of the enumeration.
references:
- https://github.com/mdecrevoisier/EVTX-to-MITRE-Attack/tree/master/TA0005-Defense%20Evasion/T1222.001-File%20and%20Directory%20Permissions%20Modification
- https://hideandsec.sh/books/cheatsheets/page/crackmapexec
- https://www.infosecmatter.com/crackmapexec-module-library/
- https://mpgn.gitbook.io/crackmapexec/smb-protocol/enumeration/enumerate-shares-and-access
tags:
- attack.
- attack.t
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  service: security
detection: # full command: cme smb -u user -p password --shares
  selection_baseline:
    EventID: 5145

  selection_pipes:
    ShareName: '\\*\IPC$'
    RelativeTargetName:
      - srvsvc # May also be triggered by other tools like SharpHound, DonPapi, ...
      - svcctl # May also be triggered by other tools like Tchopper

  selection_admin_share:
    ShareName: '\\*\ADMIN$'
    RelativeTargetName: # RelativeNames with high entropy (eg: nESNaYmfIO, srnCKoBLQW...)

  filter:
    IpAddress: '%administration_hosts%' # List of IPs of your administration host to reduce false positive

  condition: selection_baseline and not filter and (selection_pipes or selection_admin_share) | count(Computer) by IpAddress > 20
  timeframe: 15m
falsepositives:
- Administrator activity, backup solutions, Windows Server Manager
level: medium

Stages and Predicates

Stage 0: `condition`

selection_baseline and not filter and (selection_pipes or selection_admin_share) | count(Computer) by IpAddress > 20

Stage 1: `selection_baseline`

selection_baseline:
  EventID: 5145

Threshold: > 20

Stage 2: `not filter`

filter:
  IpAddress: '%administration_hosts%'

Stage 3: `selection_pipes`

selection_pipes:
  ShareName: '\\*\IPC$'
  RelativeTargetName:
    - srvsvc
    - svcctl

Stage 4: `selection_admin_share`

selection_admin_share:
  ShareName: '\\*\ADMIN$'
  RelativeTargetName:

Exclusions

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

Field	Kind	Excluded values
`IpAddress`	eq	`%administration_hosts%`

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
`RelativeTargetName`	eq	`srvsvc` corpus 2 (sigma 2) `svcctl` corpus 6 (sigma 5, kusto 1)
`RelativeTargetName`	is_null	(no value, null check)
`ShareName`	wildcard	`\\\ADMIN$` corpus 6 (sigma 6) `\\\IPC$` corpus 11 (sigma 11)

`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)

CrackMaxpExec share permission enumeration

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_baseline`

Stage 2: `not filter`

Stage 3: `selection_pipes`

Stage 4: `selection_admin_share`

Exclusions

Indicators

Keyboard shortcuts

Search operators

CrackMaxpExec share permission enumeration

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_baseline

Stage 2: not filter

Stage 3: selection_pipes

Stage 4: selection_admin_share

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_baseline`

Stage 2: `not filter`

Stage 3: `selection_pipes`

Stage 4: `selection_admin_share`