I’ll have to take your word on our capabilities, as that stuff is heavy for me !
Russia and NK are very overt with their cyber capabilities and have open;y used it; China less so in terms of public use although they've good capabilities.
The West (US, UK, France and Israel) have the capabilities and do use them, but it's more subtle. I'd be surprised if it isn't being used right now to some extent.
If they went for the cables or satellites, which the Russians have focused their development on, it'd cross the line and there's no way we wouldn't respond.
They need it now more than ever, so it would be a bad choice. If you have a little google around you can see how the internet traffic is changing direction!
On another note, there's a fair few unconfirmed videos of Russian armour and air assets being knocked out, so it's hopefully not the walk over some want.