These are points where one protocol is translated to another. Mainly in our study they are points where TCP/IP traffic is converted to some (often proprietary) control protocol such as Modbus, LonWorks, BACNet, etc. These other protocols are often industry specific and there are too many serving different purposes to list them all here. We are interested in these bridges because they are specifically places where an automation or control network connects to an IP network. Thus it is a great place to look for the internet connectivity of an industrial system. [Devices]