I have heard suggestions here to have an offline computer where keys are stored. Even transactions that need to be paid can be saved, entered into the offline computer, signed, and the confirmation transferred back to the flashdrive to be uploaded to the internet. But this requires a flashdrive to go back and forth. So how much does that compromise security?
If one only transmits specific files back and forth to the flashdrive, is it safe? Or is it possible for a program to install itself unknowingly on the flashdrive while in the internet-connected computer?
First of all, there's no need to be so scared and overprotective. It all depends on how much money you're storing and how secure is your network and apartment.
I've been using hardware wallets on my online computers for many years with no problems.
You can safely store coins on your pc, even if it's online. You only have to remember about basic security measures (link clicking, opening attachments, entering suspicious sites), have good anti virus software and never store your passwords on your pc.
If you're determined to use an offline PC, connecting it for a minute to send transaction is perfectly safe and nobody will have time to hack you in those 2 minutes that you need to pay and disconnect.
So turning off the Wifi using the linux GUI is relatively safe in terms of knowing that it is actually turned off? I am planning on downloading and installing some basic software on a clean laptop and will then turn off the Wifi, generate encrypted passwords, and then later perhaps not connect to the internet, or maybe infrequently as you have mentioned.
If you desperately want to use SD Cards or USB drives/flash drives go out and by three high quality ones
The smartest thing i have heard today. I recommend the same approach, but instead of flash drive can be used quality CD+R disk. You can add information to it, with no afraid to erase previous session.
How long will a CR+R disk last compared to a flashdrive?