This question already has an answer here:
So it seems like all of the security solutions mentioned so far are focused on preventing double spend attacks.
But what about attacks that aren't motivated by actually successfully double spending?
What if, for example, a government entity or a malicious hacker group or a hedge fund wanted to simply grind IOTA to a halt for no direct monetary gain of its own?
Without the central Coordinator, couldn't such a group just spam hundreds of thousands of conflicting transactions at random nodes in the tangle? Sure, there's a tiny bit of proof of work involved in every transaction, but it's supposedly minimal enough that a battery powered IoT device can handle it.
In this scenario, wouldn't legit transactions pile up on top of all of the bad actor conflicting transactions? Then when enough nodes discovered the conflicting transactions, they'd have to discard all of the legit transactions as well. It's easy to imagine these conflicting transactions covering the tangle in muck, making it so few legit transactions could get through (and would therefore have to be reissued).
Without a central coordinator preventing such an attack, what's there to prevent it? Again, this has nothing to do with double spending.