A kerberoasting attack targets Active Directory to steal password hashes of service accounts. Attackers exploit the Kerberos authentication protocol to request service tickets for Service Principal Names (SPNs) and crack them offline. This method requires minimal privileges and can be launched by any domain user, making it a significant threat. In this article, we’ll break down how kerberoasting works, why it’s dangerous, and how to detect and prevent such attacks.
What is Kerberoasting
Kerberoasting is a sophisticated attack technique aimed at extracting password hashes of Active Directory accounts linked with Service Principal Names (SPNs). Attackers leverage the Kerberos authentication protocol to request a Kerberos ticket for an SPN, accessing the encrypted service account password without requiring elevated privileges. This makes Kerberoasting a potent tool in the attacker’s arsenal, as it can be initiated by any authenticated domain user, making it a pervasive threat in Active Directory environments.
The attack is executed offline, allowing attackers to crack the password hash at their leisure, far from the prying eyes of network defenses. This method allows attackers to repeatedly attempt to crack the password without triggering suspicious activity alerts.
SPNs tied to user-created passwords are particularly vulnerable, as these passwords often lack the complexity of those tied to host-based accounts, making them easier to crack.
The Basics of Kerberos Authentication Protocol
At the heart of Kerberoasting lies the Kerberos authentication protocol, a robust system designed to authenticate users within a network. This protocol consists of two main components: the Authentication Server (AS) and the Ticket Granting Server (TGS). When a user logs in, the Key Distribution Center (KDC) generates a logon session key and a Ticket Granting Ticket (TGT). The TGT is crucial because it authenticates users and grants them access to network resources without repeatedly prompting for passwords.
Once a user is authenticated, the TGT is presented to the Ticket Granting Server (TGS), which validates the TGT and issues service tickets for accessing specific services. These service tickets are encrypted with the hash of the service account’s password, forming the basis for Kerberoasting attacks. Understanding the mechanics of Kerberos authentication highlights how attackers exploit this protocol to gain unauthorized access.
The Kerberos service ticket is a linchpin in this process, as it allows authenticated users to access various network services seamlessly. However, this convenience comes with a risk. Attackers can request these service tickets for SPNs, gaining access to the encrypted service account password.
Focusing on the Kerberos authentication protocol reveals the interplay between security and vulnerability that Kerberoasting exploits.
Service Principal Names (SPNs) in Active Directory
Service Principal Names (SPNs) serve as unique identifiers in AD. They connect a service instance with a logon account. These identifiers are essential for issuing service tickets, as they enable the authentication process within the network. However, this critical role also makes SPNs prime targets for attackers engaging in Kerberoasting attacks. Attackers exploit SPNs to retrieve encrypted service tickets and work on cracking the service account’s password offline, using the service principal name SPN.
Not all Active Directory accounts have SPNs; typically, only service accounts are assigned SPNs, protecting standard user accounts to some extent. However, high-privilege service accounts with SPNs are particularly attractive targets due to their connection to critical services and potential for elevated access, especially when considering the implications of an AD account.
Regular audits and removing unnecessary SPNs can minimize potential attack vectors, enhancing overall security.
What is a Kerberoasting Attack
Kerberoasting attacks target the intricate Kerberos authentication process to extract password hashes from AD user accounts. The objective is simple yet effective: extract a Kerberos service ticket and crack it to obtain the user’s password hash. The typical process involves gaining initial access, scanning for vulnerable SPNs, requesting service tickets, and finally, extracting and cracking these tickets.
After authentication, attackers request a Ticket Granting Service (TGS) ticket for a specific service, setting the stage for the subsequent steps in the attack. Each step in the Kerberoasting attack leverages the inherent mechanics of the Kerberos protocol, demonstrating the need for robust security practices to defend against such tactics.
Step 1: Initial Access with Domain User Account
The first step in a Kerberoasting attack involves gaining initial access with a domain user account. Attackers exploit the privileges associated with regular domain user accounts to initiate the attack. These accounts, while not having elevated privileges, are sufficient to request service tickets for SPNs, making them an ideal starting point for attackers. Using the same access level as a legitimate user allows attackers to blend in with normal network activity, making detection more challenging.
With initial access secured, attackers can query Active Directory to identify potential targets. The legitimacy of the user’s identity provides a cloak of normalcy, allowing attackers to operate without raising immediate suspicion. This initial access is crucial for setting up the subsequent stages of the Kerberoasting attack.
Step 2: Identifying Vulnerable SPNs
Once initial access is achieved, the next step is identifying vulnerable SPNs. Attackers scan for SPNs linked to accounts with the necessary permissions to be exploited. They look for service-related accounts associated with elevated privileges, as these accounts often have weaker passwords and higher-value access. Automated tools significantly increase the efficiency of this scanning process, enhancing the attacker’s ability to identify kerberoastable accounts quickly.
During this phase, attackers may also target accounts based on specific attributes like adminCount and group memberships, as well as factors like last login times. By refining their targets, attackers can maximize the chances of successfully obtaining valuable service tickets.
Step 3: Requesting Service Tickets
With vulnerable SPNs identified, attackers proceed to request service tickets. They impersonate an account user with an SPN and request a Kerberos service ticket for that SPN. This process involves the authenticated domain user requesting a Kerberos ticket, which is then encrypted with the hash of the service account password. Tools like Impacket’s GetUserSPNs, Rubeus, and PowerSploit are often used to facilitate this step.
The purpose of requesting these tickets is to obtain the user’s password hash, which can then be subjected to brute force attacks. Extracting the service ticket lays the groundwork for the next phase of the attack.
Step 4: Extracting and Cracking Service Tickets
In the final stage of a Kerberoasting attack, attackers extract and crack the service tickets obtained in the previous step. Tools like Mimikatz and Rubeus can be used to extract TGS tickets from memory without needing administrator privileges. This allows attackers to operate under the radar, avoiding detection by conducting the cracking process offline.
Offline brute force methods are preferred for cracking service tickets, as they evade detection by keeping the activity off the network. Password cracking tools such as Hashcat or John the Ripper might be used to obtain the plaintext password from cracked tickets.
Once the plaintext credentials are obtained, attackers can gain access to unauthorized networks and assets typically available to legitimate account owners.
Detecting Kerberoasting Attacks
Detecting Kerberoasting attacks is crucial for protecting network security. Credential-based attacks like Kerberoasting can be challenging to identify due to the legitimate nature of the initial access. AD Monitoring and detection tools, although not foolproof, play a vital role in identifying potential Kerberoasting activities. Solutions like Windows Event Log and SIEM tools can help track unusual behaviors and link network activities to user identities.
To enhance detection, it’s important to monitor for unusual patterns in TGS requests and identify abnormal behaviors in network activity. Despite the high levels of false positives, taking additional steps beyond standard practices can improve detection accuracy and aid in timely response to potential attacks.
Monitoring Event IDs 4768 and 4769
Monitoring specific Event IDs is crucial for detecting Kerberoasting activities. Event ID 4769 logs when a Kerberos service ticket (TGS) is requested, providing valuable insights into potential suspicious activities. Additionally, monitoring failed service ticket requests and unusual service ticket requests can help identify potential Kerberoasting attempts.
To effectively detect these activities, enable ‘Audit Kerberos Service Ticket Operations’ under Group Policy on Domain Controllers. It’s important to note that Security Event IDs 4768 and 4769 are not enabled by default and must be configured manually. By ensuring these Event IDs are monitored, organizations can significantly enhance their ability to identify and respond to Kerberoasting attacks.
Identifying Unusual TGS Requests
Identifying unusual TGS requests is key to detecting Kerberoasting attempts. Monitoring Event ID 4769 is essential for spotting suspicious activities related to TGS requests. The Ticket Encryption Type associated with Kerberoasting detection is 0x17 (RC4-HMAC), a common indicator of such attempts.
Excessive requests by a single user for multiple TGS tickets can indicate suspicious activity related to Event ID 4769. Typically, users generate 10 to 20 Kerberos TGS requests per day, so requests significantly above this threshold should be investigated. Analysts should also correlate PowerShell activity related to Kerberos requests with high-privilege accounts to gain insights into potential Kerberoasting activities.
Using Deception for Detection
Using deception techniques can enhance the detection of Kerberoasting attempts. Setting up a deception involves linking an SPN to a non-existent service to lure potential attackers. These decoy systems, or honeypots, are designed to attract and trap hackers attempting to exploit vulnerabilities.
- How deception technology works
- Following effective deception methods
- Outsmart changing threats
Observing interactions with these SPNs helps security teams identify potential Kerberoasting attempts and gain valuable insights into attacker behavior. Successful detection of unauthorized access attempts through honeypots can enhance security measures against future Kerberoasting attacks.
Preventing Kerberoasting Attacks
Preventing Kerberoasting attacks requires a multi-faceted approach. Here are some essential strategies to mitigate Kerberoasting risks:
- 1. Implement strong password policies.
- 2. Utilize Group Managed Service Accounts (gMSAs).
- 3. Regularly audit Active Directory accounts.
- 4. Educate staff on identifying phishing attempts.
- 5. Teach staff to create strong passwords.
- 6. Encourage reporting of suspicious activities.
Weak passwords and outdated encryption methods significantly increase the risk of such attacks. Educating staff plays a crucial role in prevention.
Strengthening overall security posture and enforcing best practices for securing Kerberos authentication, such as disabling unnecessary protocols and using encryption, can significantly reduce vulnerabilities. Implementing AES as the encryption standard can mitigate the effectiveness of Kerberos attacks.
Enforcing Strong Password Policies
Enforcing strong, complex passwords is a cornerstone in defending against Kerberoasting attacks. The strength of a password directly impacts the success of an attack, with weak passwords allowing attackers to easily obtain service account credentials and escalate privileges. Strong passwords should be more than 25 characters long and include a mix of letters, numbers, and special characters, making them significantly harder to crack. A password of this complexity could take years or even centuries to crack, providing a robust defense against brute force attacks.
Regularly rotating passwords, ideally every 30 days or less, further reduces the risk of exposure. Admin accounts, often targeted due to weaker password policies, should follow stringent password rules to prevent potential Kerberoasting attacks.
Disabling unnecessary protocols like NTLM can also reduce the attack surface. By focusing on password hygiene, organizations can fortify their defenses against offline brute force attacks aimed at cracking password hashes.
Implementing Managed Service Accounts (MSAs)
Managed Service Accounts (MSAs) and Group Managed Service Accounts (gMSAs) are vital tools in the fight against Kerberoasting attacks. By automating password management, MSAs and gMSAs ensure strong password hygiene and reduce the window of opportunity for attackers. These accounts automatically change their passwords every 30 days or less, making it difficult for attackers to exploit the same credentials over an extended period. The service account’s automated features enhance security measures significantly.
Implementing MSAs and gMSAs helps maintain secure service accounts by enforcing regular password rotations and minimizing the risk of weak passwords. This automated approach not only strengthens security but also reduces the administrative burden of manual password management. Leveraging managed service accounts helps organizations better protect their Active Directory environments from Kerberoasting attacks.
Regularly Auditing Active Directory Accounts
Regularly auditing Microsoft Active Directory accounts is crucial for identifying and mitigating vulnerabilities that could be exploited in Kerberoasting attacks. Regular audits help organizations identify weak passwords and ensure that security measures are up-to-date. These audits help to uncover weak points in the network, allowing for timely remediation and strengthening overall defenses.
Maintaining strong security measures through regular audits significantly reduces the risk of Kerberoasting attacks. It involves reviewing service account passwords, ensuring compliance with strong password policies, and removing unnecessary SPNs. By keeping Active Directory accounts secure, organizations can minimize potential attack vectors and enhance their network security posture.
Response Plan for Kerberoasting Incidents
Having a response plan in place is vital for quickly identifying and mitigating Kerberoasting attacks. While the signs of a Kerberoasting attack cannot definitively confirm that an attack has occurred, unusual service ticket requests and unauthorized access attempts are strong indicators. A response plan should aim to quickly identify the extent of the attack and take steps to mitigate damage, such as patching vulnerabilities and updating security policies.
Common indicators of compromise include a spike in service ticket requests and unusual network traffic patterns. After detecting a Kerberoasting attack, it’s essential to review and update password policies for strength and security.
A robust response plan enables organizations to effectively manage and recover from Kerberoasting incidents, minimizing the impact on their networks.
Disabling Compromised Accounts
Immediately disabling compromised accounts is a critical step in responding to a Kerberoasting incident. Removing access to these accounts helps organizations prevent further unauthorized actions and limit the damage. Promptly disabling compromised accounts helps to contain the attack and protect sensitive data from being accessed by attackers.
In addition to disabling compromised accounts, it is important to investigate how the accounts were compromised and take steps to prevent future incidents. This includes reviewing account credentials and implementing stronger security measures to safeguard against similar attacks in the future.
Swift action enables organizations to effectively respond to Kerberoasting incidents and protect their networks from further compromise.
Changing Service Account Passwords
Changing service account passwords is a critical step in securing the environment after detecting a Kerberoasting attack. Timely updates to service account passwords ensure that any stolen credentials are rendered useless, preventing attackers from gaining further access. This involves changing all passwords associated with the compromised accounts and implementing stronger password policies to prevent future breaches.
Updating service account passwords should be done immediately after detecting an attack to minimize the risk of further exploitation. Ensuring that passwords are complex and regularly rotated enhances defenses against Kerberoasting attacks and protects networks from unauthorized access.
Reviewing Logs and Notifying Affected Users
Reviewing logs is a crucial part of the response process during a Kerberoasting attack. Analyzing network logs helps organizations identify suspicious activities and understand the extent of the attack. This helps in determining the scope of the breach and identifying any additional compromised accounts.
Notifying affected users and stakeholders about the breach is also essential. Transparency in communication ensures that all parties are aware of the incident and can take necessary precautions to protect their data. Keeping users informed helps organizations maintain trust and collaborate effectively to mitigate the attack’s impact.
Fidelis Active Directory Intercept™: A Complete AD Security Solution
As the central repository for all privileged information, AD is a prime target for hackers. It functions like the security vault of a wealthy household, safeguarding the family’s most valuable assets. If attackers compromise AD, they gain control over the entire network, enabling them to steal data effortlessly and move undetected. This is how something like a Kerberoasting attack takes over as well.
Fidelis Active Directory Intercept™ combines AD-aware network detection and response (NDR) platform and integrated Active Directory deception technology with foundational AD log and event monitoring to not just identify Microsoft Active Directory threats – but to respond swiftly. This solution can help you protect your most crucial assets from kerberoasting attacks and others like it.
Conclusion
In summary, understanding and defending against Kerberoasting attacks is crucial for maintaining the security of Active Directory environments. By recognizing the mechanics of Kerberos authentication, the role of SPNs, and the step-by-step process of a Kerberoasting attack, organizations can better prepare for and prevent such threats. Implementing strong password policies, leveraging managed service accounts, and conducting regular audits are key strategies in mitigating the risk of Kerberoasting attacks.
A robust response plan, including disabling compromised accounts, changing passwords, and reviewing logs, ensures that organizations can effectively manage and recover from incidents. By staying vigilant and proactive, you can protect your network from Kerberoasting attacks and maintain a secure environment. Take these insights and apply them to strengthen your cybersecurity defenses today.
Frequently Ask Questions
What is a Kerberoasting attack?
A Kerberoasting attack targets Active Directory accounts with Service Principal Names (SPNs) to extract password hashes, enabling attackers to crack these passwords offline and potentially gain unauthorized access.
How do attackers gain initial access for a Kerberoasting attack?
Attackers gain initial access for a Kerberoasting attack by leveraging the privileges of a standard domain user account to request Kerberos service tickets for service principal names (SPNs). This approach does not require elevated privileges, making it an accessible entry point.
How can organizations detect Kerberoasting attacks?
Organizations can effectively detect Kerberoasting attacks by monitoring Windows Event Log IDs 4768 and 4769 for unusual patterns in TGS requests and employing deception techniques such as honeypots. This proactive approach enhances security against potential threats.
What are some preventive measures against Kerberoasting attacks?
To prevent Kerberoasting attacks, enforce strong password policies, implement Managed Service Accounts (MSAs), regularly audit Active Directory accounts, and educate staff on cybersecurity best practices. These measures significantly enhance your security posture against such threats.
What should be included in a response plan for Kerberoasting attacks?
A comprehensive response plan for Kerberoasting attacks should include disabling compromised accounts, changing service account passwords, reviewing logs for suspicious activities, and notifying affected users to effectively mitigate the attack’s impact.
