Final answer:
A Kerberoasting attack is performed when a penetration tester has gained access to a network with Kerberos authentication and aims to crack service account passwords in hopes of lateral movement or privilege escalation.
Step-by-step explanation:
You would perform a Kerberoasting attack in a situation where you have access to a network that uses Kerberos authentication and you want to crack the service account passwords. This attack specifically targets service accounts because they often have strong privileges and their passwords are less likely to be changed regularly. A penetration tester may choose to perform Kerberoasting after gaining initial access to perform lateral movement within the network or to escalate privileges by compromising high-value service accounts.