Selah discovers that a member of her organization's staff has installed a remote access Trojan on their accounting software server and has been accessing it remotely. What type of threat has she discovered?

Selah has found an insider threat. Insider threats can be hard to find, as a malicious administrator or other privileged users will often have the ability to conceal their actions or may actually be the person tasked with hunting for threats like this! This is not a zero-day—no vulnerability was mentioned, there was no misconfiguration since this was an intentional action, and encryption is not mentioned or discussed.