My thinking and motives are a bit different than what people have discussed here. I have a laptop that I use to access the internet. I go everywhere with it. The computer I use to record my music is a desktop. I only access certain types of sites with the desktop machine. I use it to access sites like the cakewalk store or my bank account. Things of that nature. I update the machine with all the latest updates.
When I record music everything is streamed to an external hard drive so in the slim chance that I do get a virus or something happens to my computer, I don't lose my work. I also backup my projects to another external hard drive in the event that my other external hard drive crashes. I have backups for my backups and I don't use a cloud service for backing up my recording projects.
Now before record music I disconnect from the internet via device manager. I also take the time to turn off all the programs that run in the background that are not needed while I am recording music. This includes programs that start up when I turn on the computer. Programs like Microsoft security, virus software, Google chrome, Roxio CD burning software ect. are all turned off
Then I turn off services I don't need that run in the background. This is anything that is internet related and things like disk defragmenter. It is really disappointing to record music and have things like this go off in the background. Then I reboot my computer.
The main reason for going to all this trouble is because it frees up the processor and ram. This action provides me with more system resources to do the things I want to do. By taking the time to do this I can use more effects and I don't need to freeze tracks because my processor can now handle everything I throw at it. Projects that have 50 tracks or more respond better when all the system eating resources are turned off.
As far as viruses go I don't go to sites where I would get a virus. My other computer is used for my main internet surfing and things like skype.
Every year I will re-image the hard drive and restore everything. I usually do this before I upgrade to the next cakewalk product. The end result is my machine works great and my projects are protected. I get a better performance from my processor when I record, mix, and master my music. when I am done recording I turn everything back on again.
This system has worked very well for me and while some people may find it unorthodox it does work well for me. I do the same thing when I edit videos.
On another point if your recording computer is connected to the internet have some fun with it. I named my router YourDogPoopsInMyYard. All my neighbors know who I am. It comes up every time they search for a wireless connection. Recently I changed the name to NSAsurvellanceUnit. I figured that would keep the neighbors away. Of course, these routers are password protected.