While monitoring network traffic to his web server cluster, Mark noticed a significant increase in traffic. He checks the source addresses for inbound traffic and finds that the traffic is coming from many different systems all over the world. What should Mark identify this as if he believes that it may be an attack?

A

A distributed network scan

B

A DNS$-$based attack

C A distributed denial$-$of$-$service attack

D A denial$-$of$-$service attack