There are too many ways for viruses and loggers to get on your computer, and AV scanners too often don't catch them. It is difficult to be safe, and most of us will be compromised some day.
They can be installed through software installs, browser exploits, by holes in "safe" software already on your computer, through misconfigured firewalls, by anyone who has access to the machine. They can jump airgaps with usb sticks. And now reformatting computers doesn't always work because there are documented viruses that can write themselves to bios.
I still like paper wallets for cold storage of Uno and Btc.
Here's how a way to make cold wallets that reduces, but does not fully eliminate risk.
Find a computer that I don't use very often.
Boot it with a Linux live CD
Go to
https://cryptap.us/uno/paperwallet.htmlAfter the wallet generator loads in your browser, but before you have generated the wallet, disconnect the computer from the internet.
Finish generating the wallet and then print it. Don't store the keys on your computer.
Go back online and send your Uno to the new paper wallet address.
It's not perfect but it's all about mitigating risk. The more inconvenience you are willing to suffer (i/e not being on the internet at al) the safer you can be.
I have kids that love to play computer and online games. They are always downloading "free games" and other crap and installing viruses & spyware on the computer in the process. I know this and so I just keep those machines on a separate network and never attach a USB drive to them. The kids are forever forbidden from using my main machine, and I lock when I step away.