[tallanvor]

While a virtual machine used only to access online banking would probably work, would your friend actually stick with it? And be honest - if he wouldn't there's not much point.

The best option is education. Help him understand how the malware was installed and how he can try and prevent it from happening in the future (don't allow applications to be installed if they weren't specifically expecting it, keep their AV running - no matter what an installer says, always install Java and Adobe updates, and avoiding dodgy streaming video and proxy sites).

I recently had to help a friend clean ransomware off his system, and found a bunch of other crap while I was at it. --I think I got it all, but I still warned him that it was possible we missed something and a full format and reinstall would be safer. In his case I'm pretty sure it came from one of the many dodgy sites used to stream TV shows and such, although he had also downloaded and installed VLC from one of those sites that rebundled it with additional crap, so that could have compromised the system as well.

[benohear]

You make a good point. Though this particular friend might well stick to it - €1600 tends to focus the mind.

But to be honest, I'm asking primarily for myself and my family. I'm not sure anyone can really be sure there is no malware on their browser (via Flash zero days or what have you), especially if several members of the family use the computer. This gets much worse with teenage kids.

So gambling the entire contents of my bank account on the assumption I'm malware free isn't quite doing it for me.

That's why I'm thinking that a straightforward setup is appealing: "When I bank, I use the OS on this USB key and don't use it for anything else".

But I also wanted to know what people around here do. Simply assume their machine is clean or take further steps?