I am looking at the WD My Passport or a WD My Book.
Or the software that comes with the drive be good enough?
Good drives, I have a few of them. Crappy backup software, though. First thing I do when I get a new Passport drive is delete that software. It's a complete waste of space.
Is cloud storage safe to use? Are my cloud files at risk of becoming infected if a file becomes infected on my computer?
Dropbox has file versioning, so even if something does mess up your files stored there, you can always revert to previous good version of them. And the versioning doesn't eat into your allowed storage space.
What I would do is set the Dropbox folder to your Passport drive, then back up your files to the Dropbox folder. (paid accounts offer 1 TB of space)
That way, if something happens to your PC (hardware failure, dead main drive, etc.), you can just plug the Passport drive into another computer and keep moving along. And if something happens to your Passport drive, you can get another one, set Dropbox to sync to the new drive, and keep moving along. And if something happens to both your computer and your passport drive (fire, flood, tornado, etc), you can get another computer, and another Passport drive, then sync from Dropbox onto the new one, and keep moving along.
It is not completely wrong. Besides, what type of data are you backing up and is it possible to get into legal trouble? For example: you work from home and store by accident or as an ad-hoc transfer solution, store your work on your cloud account. In my case, I would get into serious legal trouble, even for the briefest of time that work would be on any server other my own or at the customer. You better make sure something similar doesn't apply to your personal situation when you (accidentally) mix work/private stuff using any cloud solution.
There are some of us (me) that work from home and absolutely must
store work related files in the cloud, and for them to be sharable with customers, in order to perform our jobs. And my employer was mighty glad that I have a Dropbox account with ample storage space when this happened
and made it impossible for customers to download their purchases.