User Added to Privileged Group in Active Directory

Elastic Stack Serverless Security

Identifies a user being added to a privileged group in Active Directory. Privileged accounts and groups in Active Directory are those to which powerful rights, privileges, and permissions are granted that allow them to perform nearly any action in Active Directory and on domain-joined systems.

Rule type: eql

Rule indices:

• winlogbeat-*
• logs-system.*

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://docs.microsoft.com/en-us/windows-server/identity/ad-ds/plan/security-best-practices/appendix-b—​privileged-accounts-and-groups-in-active-directory

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Persistence

Version: 5

Rule authors:

• Elastic
• Skoetting

Rule license: Elastic License v2

Privileged accounts and groups in Active Directory are those to which powerful rights, privileges, and permissions are
granted that allow them to perform nearly any action in Active Directory and on domain-joined systems.

Attackers can add users to privileged groups to maintain a level of access if their other privileged accounts are
uncovered by the security team. This allows them to keep operating after the security team discovers abused accounts.

This rule monitors events related to a user being added to a privileged group.

• Identify the user account that performed the action and whether it should manage members of this group.
• Contact the account owner and confirm whether they are aware of this activity.
• Investigate other alerts associated with the user/host during the past 48 hours.

• This attack abuses a legitimate Active Directory mechanism, so it is important to determine whether the activity is
  legitimate, if the administrator is authorized to perform this operation, and if there is a need to grant the account
  this level of privilege.

• Initiate the incident response process based on the outcome of the triage.
• If the admin is not aware of the operation, activate your Active Directory incident response plan.
• If the user does not need the administrator privileges, remove the account from the privileged group.
• Review the privileges of the administrator account that performed the action.
• Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
• Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
  mean time to respond (MTTR).

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate event.ingested to @timestamp for this rule to work.

iam where event.action == "added-member-to-group" and
  group.name : ("Admin*",
                "Local Administrators",
                "Domain Admins",
                "Enterprise Admins",
                "Backup Admins",
                "Schema Admins",
                "DnsAdmins",
                "Exchange Organization Administrators")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Account Manipulation
  • ID: T1098
  • Reference URL: https://attack.mitre.org/techniques/T1098/