How is a Distributed Denial of Service (DDOS) attack distinguished from a regular DOS attack?

In a Distributed Denial of Service attack, a large number of compromised systems - often organized into a botnet - simultaneously flood a single target with traffic, overwhelming its resources. This distributed origin is the defining characteristic separating DDoS from a standard DoS, which originates from a single source. The use of many distributed hosts also makes mitigation far more difficult because traffic arrives from numerous different IP addresses.

DDoS attacks concentrate traffic from many distributed sources onto one target - the distribution describes the attack origin, not multiple targets.

A standard DoS attack can target any networked device or service and is not limited to a single router.

A DDoS attack overwhelms a specific host or service, not the entire Internet.