Please explain how the sophisticated August 2014 Monero network spam attack was designed and conducted.
How did the Monero core team respond to the attack and prevent any lasting damage?
You'll find an extensive analysis here.
The tl;dr version is that the attacker exploited an obscure edge-case bug to fork the network. The fork was the intention and the net-effect. The devs promptly notified the community and the exchanges and released a fix.