Security implications of publicly reachable building automation systems

In a connected world Internet security is becoming increasingly important. Attacks, which are frequently executed by botnets, can impact people in their everyday life. A ubiquitous kind of attack is the amplification attack, a special type of Denial-of-Service attack. Several protocols such as DNS, NTP, and SNMP are known to be vulnerable to amplification attacks when security practices are not followed. In this work we evaluate the vulnerability of BACnet, a building automation and control protocol, to amplification attacks. To assess BACnet's vulnerability we conduct active traffic measurements on an Internet-wide scale. We find 16 485 BACnet devices, the largest number to date. Additionally, more than 14 k of these devices can be misused as amplifiers, with some generating amplification factors up to 120. To remediate this potential threat we employ a vulnerability notification campaign in close coordination with a CERT. Finally, we also give suggestions to thwart the amplification attack potential of BACnet.