A distributed denial-of-service (DDoS) attack is a deliberate attempt to make a server, an online service, or a network unavailable by overwhelming the target with an excessive amount of traffic from multiple sources. This can be done by using a large number of infected computers or devices (known as botnets) to simultaneously send requests or traffic to the target, overwhelming it to the point where it becomes unable to respond to legitimate requests.
DDoS attacks can severely disrupt online operations, leading to downtime, slowdowns, or malfunctions of services, affecting businesses, websites, and even entire networks. These attacks can be motivated by various reasons, ranging from simple online vandalism to economic or political sabotage.
The techniques to counter these attacks include the use of firewalls, DDoS mitigation services, and network traffic monitoring to identify and block suspicious or abnormal traffic.