Potential Privilege Escalation via Local Kerberos Relay over LDAP

Elastic Stack Serverless Security

Identifies a suspicious local successful logon event where the Logon Package is Kerberos, the remote address is set to localhost, and the target user SID is the built-in local Administrator account. This may indicate an attempt to leverage a Kerberos relay attack variant that can be used to elevate privilege locally from a domain joined limited user to local System privileges.

Rule type: eql

Rule indices:

• winlogbeat-*
• logs-system.*

Severity: high

Risk score: 73

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://github.com/Dec0ne/KrbRelayUp
• https://googleprojectzero.blogspot.com/2021/10/using-kerberos-for-authentication-relay.html
• https://github.com/cube0x0/KrbRelay

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Privilege Escalation
• Credential Access

Version: 1

Rule authors:

• Elastic

Rule license: Elastic License v2

authentication where

 /* event 4624 need to be logged */
 event.action == "logged-in" and event.outcome == "success" and

 /* authenticate locally via relayed kerberos ticket */
 winlog.event_data.AuthenticationPackageName : "Kerberos" and winlog.logon.type == "Network" and
 source.ip == "127.0.0.1" and source.port > 0 and

 /* Impersonate Administrator user via S4U2Self service ticket */
 winlog.event_data.TargetUserSid : "S-1-5-21-*-500"

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Privilege Escalation
  • ID: TA0004
  • Reference URL: https://attack.mitre.org/tactics/TA0004/

• Technique:

  • Name: Abuse Elevation Control Mechanism
  • ID: T1548
  • Reference URL: https://attack.mitre.org/techniques/T1548/

• Sub-technique:

  • Name: Bypass User Account Control
  • ID: T1548.002
  • Reference URL: https://attack.mitre.org/techniques/T1548/002/

• Tactic:

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

• Technique:

  • Name: Steal or Forge Kerberos Tickets
  • ID: T1558
  • Reference URL: https://attack.mitre.org/techniques/T1558/