A DDoS attack essentially tries to down a website or internet service by bombarding the system with a flood of data traffic. To do so, the hacker can sometimes harness botnets, or armies of malware-infected computers, to generate the traffic.

In this case, the attack originated from “70,000 sources” based in countries across Asia and the US, Microsoft says. Whether the hacker used a botnet was left unsaid. But the UDP protocol was exploited in what’s known as a “reflection attack” to amplify the data traffic to 2.4Tbps.