If Valerie knows a system is compromised, what action should she take to prevent further impact to the network?

When a system is known to be compromised, the most immediate and effective action is to isolate the system from the network. This measure prevents the potential spread of malware or malicious activity to other devices on the network and helps safeguard sensitive data. By cutting off network access, Valerie can contain the threat, thereby limiting any further impact on the system and the overall network.

Taking this action allows for a more controlled approach to investigating and remediating the compromise. It minimizes the risk of the attacker gaining additional access or using the compromised system as a launching point for attacking other systems in the environment.

Activities like rebooting the system, updating antivirus software, or running a vulnerability scan are important in managing a security breach, but they do not address the immediate risk of further compromise and potential damage to the network. Rebooting might temporarily disrupt a malware's operation, but it does not resolve the core issue of an active compromise. Updating antivirus software can be helpful, yet if the system remains connected to the network, it risks spreading the infection. Similarly, running a vulnerability scan is part of identifying weaknesses and assessing the situation, but again, this should come after ensuring the system is isolated to prevent further damage.