Bob, a professional hacker, wanted to eccouncil video

Full Certification Question

Bob, a professional hacker, wanted to maintain persistence within a compromised ICS network. For this purpose, he manipulated the variables required for the functioning of programmable logic controllers (PLCs) with malicious code to retain access to the network even after the compromised device is restarted. Which of the following techniques did Bob employ to maintain persistence on the target ICS network?