In NetCat, what does Zero-I/O mode (-z) achieve?

• A. Sends no data and just probes for open ports
• B. Sends a stream of data with no acknowledgement
• C. Establishes a reverse shell
• D. Logs all activity to disk

Answer: (A)

Zero-I/O mode in NetCat is used for quick port discovery. It tells nc to attempt connections to the specified ports but not to send any data after the connection is made, and to close the connection immediately if the port is open. This lets you determine which ports are listening without transferring a payload or establishing a full session. That’s why the option described as sending no data and just probing for open ports is the best fit. The other behaviors—establishing a reverse shell, logging activity, or sending a continuous data stream—aren’t what this mode does.