# Can network monitoring break our PLCs?

Passive monitoring cannot, because it only listens to a copy of the traffic and never sends anything to the controllers. Active scanning is a different matter: some older PLCs and remote terminal units crash, reboot or drop into a fault state when a discovery tool or vulnerability scanner probes them, which is why many plants keep scanners off the control network. Take the copy from a SPAN port on an industrial switch or from a passive network TAP, and check with the switch vendor that mirroring will not overload an old switch. NetSenX reads Modbus/TCP, DNP3, BACnet/IP, EtherNet/IP and S7comm from passive capture, from the Pro plan, and never actively probes devices classified as OT. Nothing is installed on the controllers and none of their settings change.

FAQ: [OT and IoT](https://netsenx.com/en/faq/ot) · https://netsenx.com/en/faq/can-network-monitoring-break-plcs

## Read next

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

## Related questions

- [Do IoT devices such as cameras and printers need monitoring?](https://netsenx.com/en/faq/do-iot-devices-need-monitoring)
- [Are cameras on their own VLAN still a risk?](https://netsenx.com/en/faq/are-cameras-on-their-own-vlan-still-a-risk)
- [How do I detect attacks on PLCs in a small factory?](https://netsenx.com/en/faq/how-to-detect-attacks-on-plcs-in-a-small-factory)
- [Why is Modbus considered insecure?](https://netsenx.com/en/faq/why-is-modbus-insecure)
- [How do I know if an unauthorised computer writes to our PLC?](https://netsenx.com/en/faq/how-to-know-if-an-unauthorised-computer-writes-to-a-plc)