Kaspersky labs released a report on Industrial and Control System (ICS) security trends. The data was reported to be gathered using Kaspersky Security Network (KSN), a distributed antivirus network.

https://ics-cert.kaspersky.com/reports/2017/03/28/threat-landscape-for-industrial-automation-systems-in-the-second-half-of-2016/

The report is here – https://ics-cert.kaspersky.com/wp-content/uploads/sites/6/2017/03/KL-ICS-CERT_H2-2016_report_FINAL_EN.pdf

The rising trend is partly due to the isolation strategy currently being followed for ICS network security no longer being effective in protecting industrial networks.