What will they do when a new form of fraud or a more potent way to do cyberattacks targets another online activity? Like ecommerce? Or blogs? Shut down all ecommerce sites? All blogs?
I find such measures as foolish as blocking port 25 - it works until the attackers and the software they use update itself to abuse the same thing in another way. A temporary relief that just complicates things.
If these are not toy projects, outages can get expensive (due to networks imposing penalties on nodes that don't fulfill promises, or trading getting messed up).
Shows why you somehow think running a node makes it a target for cyber attack and frauds...
How does running a node make it a target for such? They only relay publicly available information and targeting a single node doesn't really harm the network.