Joey is a network administrator. He gets a call from Melissa on the web team. She indicates that a set of servers that host an external website have become unresponsive. They decide to restart the systems. Upon examining the log files, they notice an extremely large number of requests coming into the servers at the same time. Joey is able to corroborate the large spike in traffic requests coming through the firewalls to the servers. Together they conclude that the source of the outage was the increase in traffic. Which type of attack has just occurred?

An attack requiring physical access

An attack against system hardware

Attacks that target the hardware or firmware of the device, such as a phishing attack

An attack leveraging network access