Final answer:
Mark believes the sudden rise in Kerberos server activity is due to the team of developers working late and frequently authenticating through the server, which aligns with the time the surge in activity is observed.
Step-by-step explanation:
Mark is investigating unusual Kerberos server performance and observes a surge in activity during off-hours. He notes that a team of developers is working late, which likely corresponds to the increased server activity. Kerberos is an authentication protocol, and if the developers are working on applications that require authentication, especially in a development environment where frequent logins might occur for testing, this would explain the increase in Kerberos server's activity. This might not cause immediate issues, but it's something that Mark, as a security analyst, should monitor to ensure that the server can handle the load and that these are legitimate authentication requests, not indicative of a security breach or attack.