A DoS (Denial of Service) attack is a type of cyberattack that aims to disrupt the normal functioning of a server, service, or network by overwhelming it with a large amount of traffic or requests. A DoS attack typically uses a single computer or device to launch the attack, sending TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) packets to the target server. TCP and UDP are two common protocols used to send data over the internet. TCP packets require a connection to be established between the sender and the receiver, and ensure that the data is delivered reliably and in order. UDP packets do not require a connection, and do not guarantee the delivery or order of the data. Both TCP and UDP packets can be used to flood a server with requests, consuming its resources and bandwidth, and preventing legitimate users from accessing the service.

A DDoS (Distributed Denial of Service) attack is a type of DoS attack that uses multiple computers or devices to launch the attack, creating a large network of attackers that can generate more traffic or requests than a single source. A DDoS attack often involves a botnet, which is a network of compromised computers or devices that are controlled by a malicious actor, usually through malware or hacking. The botnet can send TCP or UDP packets to the target server from different locations and IP addresses, making it harder to trace and block the attack. A DDoS attack can also target multiple servers or services that are distributed over a LAN (Local Area Network), such as a web hosting service or a cloud computing platform, affecting the availability and performance of the entire network.

The main difference between a DoS attack and a DDoS attack is the number and diversity of the sources that are involved in the attack. A DoS attack comes from a single source, while a DDoS attack comes from multiple sources. This makes a DDoS attack more powerful, faster, and harder to stop than a DoS attack.