Distributed Denial of Service (DDoS) is a type of cyberattack where multiple computers, often controlled by hackers, flood a target server or network with excessive fake traffic. This overloads the system, causing it to slow down or crash, making websites or online services unavailable to legitimate users. DDoS attacks can disrupt businesses, cause financial losses, and damage reputations. They are often carried out using networks of infected computers, known as botnets, and can be difficult to stop because the traffic comes from many sources at once.