What is Distributed Denial-of-Service (DDoS) Attack?

Similar to a Denial-of-Service (DoS) attack, a Distributed Denial-of-Service (DDoS) attack is a type of malicious network offensive conducted by a number of systems against a target. In a DDoS attack, perpetrators use traffic from many different sources to flood a connected machine or service with requests in an effort to overwhelm its network and make it unavailable for use. Because multiple traffic sources are more difficult to identify, DDoS attacks are significantly more challenging to combat than DoS attacks.