Service information is not encrypted when transmitted as BACnet packets
over the wire, and can be sniffed, intercepted, and modified by an
attacker. Valuable information such as the File Start Position and File
Data can be sniffed from network traffic using Wireshark's BACnet
dissector filter. The proprietary format used by WebCTRL to receive
updates from the PLC can also be sniffed and reverse engineered.
Credits
Jonathan Lee, Thuy D. Nguyen, and Neil C. Rowe of the Naval Postgraduate School reported this vulnerability to CISA.
