Suspicious LDAP-Attributes Used

Status: test
Severity: high
Log source: product windows, service security
Author: xknow @xknow_infosec
Source: github.com/SigmaHQ/sigma

Detects the usage of particular AttributeLDAPDisplayNames, which are known for data exchange via LDAP by the tool LDAPFragger and are additionally not commonly used in companies.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1001.003` Data Obfuscation: Protocol or Service Impersonation

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 5136	A directory service object was modified.

Rule body yaml

title: Suspicious LDAP-Attributes Used
id: d00a9a72-2c09-4459-ad03-5e0a23351e36
status: test
description: Detects the usage of particular AttributeLDAPDisplayNames, which are known for data exchange via LDAP by the tool LDAPFragger and are additionally not commonly used in companies.
references:
    - https://medium.com/@ivecodoe/detecting-ldapfragger-a-newly-released-cobalt-strike-beacon-using-ldap-for-c2-communication-c274a7f00961
    - https://blog.fox-it.com/2020/03/19/ldapfragger-command-and-control-over-ldap-attributes/
    - https://github.com/fox-it/LDAPFragger
author: xknow @xknow_infosec
date: 2019-03-24
modified: 2022-10-05
tags:
    - attack.t1001.003
    - attack.command-and-control
logsource:
    product: windows
    service: security
    definition: The "Audit Directory Service Changes" logging policy must be configured in order to receive events. Audit events are generated only for objects with configured system access control lists (SACLs). Audit events are generated only for objects with configured system access control lists (SACLs) and only when accessed in a manner that matches their SACL settings. This policy covers the following events ids - 5136, 5137, 5138, 5139, 5141. Note that the default policy does not cover User objects. For that a custom AuditRule need to be setup (See https://github.com/OTRF/Set-AuditRule)
detection:
    selection:
        EventID: 5136
        AttributeValue|contains: '*'
        AttributeLDAPDisplayName:
            - 'primaryInternationalISDNNumber'
            - 'otherFacsimileTelephoneNumber'
            - 'primaryTelexNumber'
    condition: selection
falsepositives:
    - Companies, who may use these default LDAP-Attributes for personal information
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 5136
    AttributeValue|contains: '*'
    AttributeLDAPDisplayName:
        - 'primaryInternationalISDNNumber'
        - 'otherFacsimileTelephoneNumber'
        - 'primaryTelexNumber'

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
`AttributeLDAPDisplayName`	eq	`otherFacsimileTelephoneNumber` `primaryInternationalISDNNumber` `primaryTelexNumber`
`AttributeValue`	match	`*`

`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)

Suspicious LDAP-Attributes Used

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

Suspicious LDAP-Attributes Used

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`