Mostly by not going there. As long as banks and CRA continue to be hacked, I am not putting my client’s information (and my firm) at risk by using all these shortcut bookkeeping apps, etc. It may take a bit longer to do the bookkeeping, but my clients appreciate the reason why I don’t use them.
I do use e-Courier when information needs to move electronically, but that is the extent of my putting client information on the net. My server is local and is backed up continually, in house.
No solution will ever be 100% hack proof, but I trust that software like TaxCycle have the security in place to function in transactions like filing a return, etc., however, this risk is mentioned in the engagement letter as well, so that clients are aware.