During a port scan, what type of devices is likely being discovered if responses are observed on TCP ports 80, 443, 515, and 9100?

The observation of responses on TCP ports 80, 443, 515, and 9100 indicates the discovery of printers or print servers in the network environment.

Port 80 is typically used for HTTP traffic, while port 443 is used for HTTPS; both may signal a web interface for management or configuration. Port 515 is associated with the Line Printer Daemon (LPD), which is used for printing services, and port 9100 is known for the raw printing protocol commonly utilized by many network printers.

When these specific ports are in response during a scan, it’s very characteristic of network printers that accept print jobs and allow management over a web interface. These ports serve specific printing protocols, further suggesting that the devices being discovered are likely printers rather than other network devices like servers, firewalls, or routers, which typically utilize different ports for their main functionalities.

In summary, responding on these particular ports strongly correlates with the presence of printers in the network.