A user reports that an air-gapped computer may have been infected with a virus after...

When dealing with a suspected virus infection on an air-gapped computer, after an initial scan with Windows Defender shows no infection, the next steps should include examining the event logs to look for suspicious activity and updating the virus definitions for a more thorough scan. Event logs can provide insights into system changes and potential malicious activities, while updated definitions ensure the antivirus software can detect the latest threats. Connecting to the network or enabling the firewall might not be appropriate due to the risk of spreading the infection, and re-imaging the computer or documenting the findings would be subsequent steps if the initial actions don't resolve the issue.References: Official CompTIA A+ Core 1 and Core 2 Student Guide​​​​.