A tool that can help Marco discover other resources on the organization's network is "netstat".
Netstat is a command-line utility that displays information about network connections and network statistics. It can be used to view active network connections, open ports, and other network-related information. Using netstat, Marco can identify other hosts on the network and services that are communicating with his system. This helps him map the network topology and identify potential attack targets. However, it is important to note that netstat may not be able to detect all network resources, and other tools may be required for a complete network assessment.