Access to a Sensitive LDAP Attribute

Elastic Stack Serverless Security

Identify access to sensitive Active Directory object attributes that contains credentials and decryption keys such as unixUserPassword, ms-PKI-AccountCredentials and msPKI-CredentialRoamingTokens.

Rule type: eql

Rule indices:

• winlogbeat-*
• logs-system.*
• logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://www.mandiant.com/resources/blog/apt29-windows-credential-roaming
• https://social.technet.microsoft.com/wiki/contents/articles/11483.windows-credential-roaming.aspx
• https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-5136

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Credential Access
• Active Directory

Version: 2

Rule authors:

• Elastic

Rule license: Elastic License v2

The 'Audit Directory Service Changes' logging policy must be configured for (Success, Failure).
Steps to implement the logging policy with Advanced Audit Configuration:

Computer Configuration >
Policies >
Windows Settings >
Security Settings >
Advanced Audit Policies Configuration >
Audit Policies >
DS Access >
Audit Directory Service Changes (Success,Failure)

any where event.action == "Directory Service Access" and event.code == "4662" and

  not winlog.event_data.SubjectUserSid : "S-1-5-18" and

  winlog.event_data.Properties : (
   /* unixUserPassword */
  "*612cb747-c0e8-4f92-9221-fdd5f15b550d*",

  /* ms-PKI-AccountCredentials */
  "*b8dfa744-31dc-4ef1-ac7c-84baf7ef9da7*",

  /*  ms-PKI-DPAPIMasterKeys */
  "*b3f93023-9239-4f7c-b99c-6745d87adbc2*",

  /* msPKI-CredentialRoamingTokens */
  "*b7ff5a38-0818-42b0-8110-d3d154c97f24*"
  ) and

  /*
   Excluding noisy AccessMasks
   0x0 undefined and 0x100 Control Access
   https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4662
   */
  not winlog.event_data.AccessMask in ("0x0", "0x100")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Credential Access
  • ID: TA0006
  • Reference URL: https://attack.mitre.org/tactics/TA0006/

• Technique:

  • Name: OS Credential Dumping
  • ID: T1003
  • Reference URL: https://attack.mitre.org/techniques/T1003/