How to prevent this1.
Don't use Windows, but we both know you're not going to change that.
Changing the OS doesn't necessarily eliminate this risk.
Such malware already has been seen in the wild for MacOS. And they can also easily exist for unix based operating systems.
I still believe checking the first and last 4-5 characters is enough.
Without doing the actual math, i am also pretty sure that this is enough to prevent such clipping board malware.
1) It is not possible for the malware to create that much addresses / store that much addresses on the victims computer without being blatantly obvious (if possible at all; i didn't do the actual math but this shouldn't be possible in a relatively short amount of time)
2) I have not seen any non plain-dumb clipping board malware yet (which doesn't mean that it doesn't exist tho).