Security in Remote programming via phone line


Thread Starter

Poirier Luc

My question is related to security in a PLC Remote programming application via phone line.

Anybody who knows the phone number ( having a PLC software) can go online and stop the PLC. How to make remote programming secure?


Bob Peterson

My practice has been to call the plant and have them connect up the modem first. After I am done I call them back and have them disconnect it.

There are more elaborate ways (such as having the modem call you back) but this is simple and will always work.

Bob Peterson

Andrew Hawdon


Depends on the PLC, some like Siemens S7 have in built security and you can require a password before being able to make online changes or before putting PLC into stop.

I agree with Bob. The plant operators have to full approval and supervision over anyone (including trusted plant staff, or consultants, or system integrators, etc.) doing on-line work from remote. Pulling the plug is about as positive as you can get!

Brian Lee Mast, P.E.
Trippel/Mast Consulting LLC
Seattle, WA
[email protected]

Andrzej Sokulski

Some modems has built in password so You can connect only with modem which has the password set. Other modems can connect only with numbers which have been set by user.
Just wondering about this remote control stuff. Would organizations connect the whole network of PLCs online? If yes, wouldn't that be dangerous as with just a single click the PLC would behave differently?