DDoS solutions aren't simple or easy.
Wikipedia explains this pretty well: https://en.wikipedia.org/wiki/Denial-of-service_attack
They use the example of a DDoS attack as:
Think of APB as the storefront. A DDoS attack blocks the door to the store. No one can get in or out, right?
What Little Orbit can do, is mitigate the attack... which includes:
Detecting the Attack
Screening the incoming requests - whether or not they are the attacking "mob" of computers, or actual player requests.
When you perform mitigation, a significant number of resources are diverted from running the server under normal conditions, to classifying, and routing traffic.
This obviously hurts the performance of the server.