Control Systems Maintenance Best Practices

Can any one share the control systems best practices to Anti Virus protection / Remote connectivity / periodic maintenance checks.

We are having Honeywell Experion PKS, ICS Triplex systems, A-B PLCs

I am sure, Mr Griffin / CWW / Ian Verhappan may be having an answer to this query. Because, i see all of them actively answering the queries flawlessly.

Thanks in advance