Kerberoasting is a post-exploitation attack technique that exploits the Kerberos authentication protocol in Active Directory (AD) environments. It enables attackers to extract encrypted service account credentials (specifically, Ticket Granting Service or TGS tickets) and crack them offline to gain unauthorized access to privileged accounts.
How Kerberoasting Works?
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Initial Access: An attacker gains access to the network using any standard domain user account.
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SPN Enumeration: The attacker enumerates Service Principal Names (SPNs) in Active Directory to identify service accounts associated with specific services.
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Requesting Service Tickets: Using the valid domain user credentials, the attacker requests service tickets (TGS) for the identified SPNs. These tickets are encrypted with the NTLM hash of the service account's password.
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Extracting Ticket Hashes: The attacker extracts the encrypted service tickets from memory or network traffic.
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Offline Cracking: The extracted tickets are then subjected to offline brute-force or dictionary attacks using tools like Hashcat or John the Ripper to recover the plaintext passwords.
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Privilege Escalation: Upon successfully cracking a service account's password, especially if it has elevated privileges, the attacker can move laterally within the network, escalate privileges, and potentially gain control over critical systems.
Why Kerberoasting Is Effective?
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Low Privilege Requirement: Any authenticated domain user can perform Kerberoasting without needing elevated privileges.
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Offline Attack: Since the password cracking is done offline, it avoids triggering real-time security alerts.
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Weak Passwords: Service accounts often have weak or non-expiring passwords, making them susceptible to brute-force attacks.
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High-Value Targets: Compromised service accounts can provide access to sensitive data and systems, especially if they have administrative privileges.
Mitigation Strategies
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Strong Password Policies: Enforce complex, lengthy passwords for service accounts and mandate regular password changes.
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Managed Service Accounts: Utilize Managed Service Accounts (MSAs) or Group Managed Service Accounts (gMSAs) that automatically handle password management.
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Limit SPN Assignments: Assign SPNs only to necessary accounts and regularly audit them to remove unnecessary entries.
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Monitor for Anomalies: Implement monitoring to detect unusual TGS requests or spikes in service ticket requests.
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Disable RC4 Encryption: Avoid using weak encryption types like RC4_HMAC_MD5 for Kerberos tickets.
Tools Commonly Used in Kerberoasting
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Rubeus: A C# toolset for Kerberos interaction and abuse.
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Impacket: A collection of Python classes for working with network protocols, including Kerberos.
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PowerView: A PowerShell tool for network situational awareness in AD environments.
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Hashcat: An advanced password recovery tool supporting various hashing algorithms.
Understanding Kerberoasting is crucial for organizations to protect their Active Directory environments. By implementing strong security practices and monitoring for suspicious activities, organizations can mitigate the risks associated with this attack vector.
