Kevin Recently Discovered That Unknown Processes Are Running in the Background

Multiple Choice

Kevin recently discovered that unknown processes are running in the background on his company's web server. During a performance review, he also noticed that the CPU is working at 80% during downtimes. Kevin believes that software is running in the background and causing the CPU to run at such a high percentage. Kevin discovers that his server along with several other computers in the company have been used to perform a DDoS on another website.  
What type of attack occurred?

A) Botnet
B) Spyware
C) Zero-day
D) DDoS