What tool can Tobias use to check whether an SMTP server is running on his Linux virtual machine?

Using Nmap is a reliable method for checking whether an SMTP server is running on a Linux virtual machine. Nmap, which stands for "Network Mapper," is a powerful open-source tool used for network discovery and security auditing. When Tobias utilizes Nmap with the appropriate command to scan for open ports, he can specifically look for port 25 (the default port for SMTP). This enables him to determine if the SMTP service is up and running on his virtual machine.

Nmap also provides additional information about the service version, which can help in assessing the security and configuration of the server. Its ability to perform various types of scans, such as TCP SYN scans, makes it particularly suited for this type of task in network security assessments.

In contrast, other tools like Wireshark are primarily focused on packet sniffing and capturing data packets on the network rather than scanning for open services. Tcpdump is another packet capturing tool that allows for network traffic analysis but does not provide a direct way to check for open services like SMTP. PsExec, a tool for executing processes on remote systems, is not relevant for checking the status of services on Linux systems.