What should an analyst's immediate response be upon discovering unauthorized software on a server?

The immediate response an analyst should take upon discovering unauthorized software on a server is to remove the unauthorized software. Removing the unauthorized software is crucial as it helps to eliminate potential risks associated with that software, such as malware, data breaches, or compromised system integrity. Acting quickly to remove such software is essential to safeguard the server and the network it resides on from further potential threats.

While investigating the source and additional steps might be necessary after ensuring the immediate safety of the system, the priority is to eradicate any unauthorized elements that could cause harm or lead to further exploitation of vulnerabilities. Additionally, shutting down the server could interrupt critical services or processes, and merely installing additional security software without first addressing the unauthorized software could allow the threat to persist or worsen. Hence, the focus should initially be on removing the threat to minimize potential damage.