Industrial control system attack modeling

Please research and describe the steps an attacker would take to compromise a Programmable Logic Controller (PLC) in an industrial environment system. Include the vulnerabilities and methods an attacker can use in each step. Use the STRIDE model to classify types of attack and ICS kill chain for each step to take. Here’s some info about what STRIDE and ICS kill chain is if you dont know what they are:
stride model info: https://en.wikipedia.org/wiki/STRIDE_(security)
ICS kill chain info: https://www.sans.org/cyber-security-summit/archives/file/summit-archive-1493413730.pdf