Kerberoasting is a sophisticated post-compromise attack technique that targets service accounts within Microsoft Active Directory environments. This method is particularly effective because it allows attackers to extract password hashes of service accounts, which are often highly privileged and have access to sensitive data.

By leveraging the Kerberos authentication protocol, attackers can request service tickets for accounts with Service Principal Names (SPNs). These tickets are then used to obtain the password hashes, which can be cracked offline. Once the plaintext credentials are obtained, the attacker can impersonate the service account, gaining unauthorized access to critical systems and data.

How does Kerberoasting Work?

Kerberoasting operates by exploiting the Kerberos authentication protocol, specifically targeting service accounts with Service Principal Names (SPNs). The attacker first compromises a domain user account, which is then used to request a service ticket from the Ticket Granting Service (TGS). This service ticket is encrypted with the hash of the service account's password.

Once the service ticket is obtained, the attacker extracts the ticket's hash and proceeds to crack it offline using tools like Hashcat or John the Ripper. This offline cracking process is crucial as it allows the attacker to avoid detection by security systems that monitor network traffic and user activity. The cracked password hash can then be used to impersonate the service account, granting the attacker unauthorized access to network resources.

What are Examples of Kerberoasting?

Examples of Kerberoasting attacks highlight the technique's effectiveness in real-world scenarios. One notable instance is the Operation Wocao, where threat actors used PowerSploit’s Invoke-Kerberoast module to request encrypted service tickets and brute-force the passwords of Windows Service Accounts offline. This allowed them to authenticate as service accounts on other systems within the network, facilitating further malicious activities.

Another significant example is the Solorigate Backdoor Incident, where APT29 threat actors obtained Ticket Granting Service (TGS) tickets for Active Directory Service Principal Names (SPNs) and cracked them offline. This method enabled unauthorized access to sensitive systems and data. Similarly, the FIN7 Threat Group utilized Kerberoasting to extract service tickets and crack passwords, allowing them to move laterally within the network and access critical credentials.

What are the Potential Risks of Kerberoasting?

The potential risks of suffering a Kerberoasting attack are significant and multifaceted. Here are some of the key risks:

• Exposure of Sensitive Data: Attackers can gain unauthorized access to sensitive information by cracking the password hashes of service accounts, which often have access to critical data.

• Privilege Escalation: Once attackers obtain plaintext passwords, they can impersonate highly privileged service accounts, escalating their access to more critical systems and data.

• Increased Attack Surface: Any authenticated domain user can request a Kerberos service ticket, creating a broad attack surface. Weak or low-complexity passwords further exacerbate this risk.

• Compromise of Critical Systems: Service accounts often have elevated permissions. Cracking these accounts can lead to the compromise of the entire Active Directory domain.

• Difficulty in Detection: Kerberoasting attacks are carried out offline, making them hard to detect with traditional security measures. Attackers can operate undetected, moving laterally within the network.

How can you Protect Against Kerberoasting?

Protecting against Kerberoasting requires a multi-faceted approach. Here are some key strategies:

• Implement Multi-Factor Authentication (MFA): Adding an extra layer of security makes it significantly harder for attackers to gain access, even if they manage to crack a password.

• Enforce Strong Password Policies: Ensure that service accounts use complex, unique passwords that are changed regularly to reduce the risk of password cracking.

• Monitor Service Ticket Requests: Keep an eye on unusually high levels of service ticket requests, which can indicate a potential Kerberoasting attack.

• Use Advanced Encryption: Enable Kerberos AES 128/256 bit encryption for service accounts to make it more difficult for attackers to crack the tickets.

• Regularly Audit Privileged Accounts: Conduct frequent audits to identify and secure privileged service accounts, ensuring they do not have excessive permissions.