# Can we see which controllers a visiting technician's laptop talked to?

Yes, if the segment the laptop used is mirrored to a sensor: every connection it made crossed the network and can be listed afterwards by its address. That answers the question plant managers and auditors ask after a visit: did the laptop touch only the machine it came for? Make this easier by giving visitors addresses from a known range or a dedicated maintenance VLAN, so their traffic is easy to tell apart from your own. On the NetSenX network map, on every plan, the laptop shows as a device with the hosts it talked to and when it was first and last seen. From the Pro plan, NetSenX also decodes Modbus/TCP, DNP3, BACnet/IP, EtherNet/IP and S7comm, so writes from a host that is not allowed to write and S7comm commands raise OT alerts. A connection made through the machine builder's own 4G router, or on an unmirrored switch inside the machine, never crosses your monitored network and is not seen.

FAQ: [OT and IoT](https://netsenx.com/en/faq/ot) · https://netsenx.com/en/faq/can-we-see-which-controllers-a-technicians-laptop-talked-to

## Read next

- https://netsenx.com/en/ot-network-monitoring
- https://netsenx.com/en/compare

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