Sandboxes are used to execute files or run applications in a controlled environment to observe their behavior without risking the main system or network. If the file is indeed a Trojan, it would exhibit malicious behavior within the isolated environment. Updating antivirus software and reviewing firewall rules may be important steps for general security hygiene but aren't specific enough actions to identify a Trojan. Reinstalling the operating system is not the best initial approach to identifying a suspected Trojan, as it is more of a last-resort action after confirming malicious activity.