Final answer:
A DoS attack comes from a single system and floods the target with traffic, while a DDoS attack employs multiple compromised systems to launch a more significant, coordinated attack, making it harder to mitigate.
Step-by-step explanation:
The main difference between a DoS (Denial of Service) attack and a DDoS (Distributed Denial of Service) attack lies in their scale and execution. A DoS attack is performed from a single computer system and aims to make a network resource unavailable to its intended users by flooding it with illegitimate requests, thereby overloading the system.
In contrast, a DDoS attack is a large-scale version of a DoS attack that originates from multiple compromised computer systems, often spread across the globe. These systems, which are infected with malware and are controlled by the attacker, work together to flood the target with a massive amount of traffic, which can be much harder to mitigate than a DoS attack.
Both attacks can have severe consequences, but due to the volume of machines involved, DDoS attacks can be more devastating and difficult to defend against. This is why organizations often implement various security measures, such as firewalls and anti-DDoS solutions, to protect against these types of cyber threats.