A Kerberoasting attack is a technique that exploits the weak encryption of Kerberos service tickets to obtain the password hashes of service accounts that have a Service Principal Name (SPN) associated with them. The attacker can then crack the hashes offline and use the plaintext passwords to impersonate the service accounts and access network resources.
A Kerberoasting attack follows these steps1:
* The attacker impersonates a legitimate Active Directory user and authenticates to the Key Distribution Center (KDC) in the Active Directory environment. They then request a Ticket Granting Ticket (TGT) from the KDC to access network resources. The KDC complies because the attacker is impersonating a legitimate user.
* The attacker enumerates the service accounts that have an SPN using tools like GetUserSPNs.py or PowerView. They then request a service ticket for each SPN from the KDC using their TGT. The KDC grants the service tickets, which are encrypted with the password hashes of the service accounts.
* The attacker captures the service tickets and takes them offline. They then attempt to crack the password hashes using tools like Hashcat or John the Ripper. They can use various methods, such as brute force, dictionary, or hybrid attacks, to guess the passwords. Alternatively, they can use a PRINCE attack, which is a probabilistic password generation technique that combines common words, patterns, and transformations to generate likely passwords2.
* Once the attacker obtains the plaintext passwords of the service accounts, they can use them to authenticate as the service accounts and access the network resources that they are authorized to.
Therefore, the next step that the analyst should take after obtaining a valid TGT is to request a service ticket for the SPN of the target service account. This will allow them to capture the service ticket and extract the password hash of the service account.
References:
* How to Perform Kerberoasting Attacks: The Ultimate Guide - StationX
* PRINCE: PRobability INfinite Chained Elements