All DDoS Definitions
DDoS Testing Definition

Fraggle Attack

A Fraggle attack is a Layer 4 reflection and amplification vector, one of the volumetric classes a thorough DDoS test is built to exercise. It is the UDP cousin of the Smurf attack: the attacker spoofs the victim's IP in UDP packets aimed at the echo (port 7) or chargen (port 19) service on a network's broadcast address. Every host on that segment that runs the service replies to the spoofed source, so a single packet fans out into a flood directed at the victim.

Fraggle attack: one spoofed packet, a whole segment replies Attacker spoofs src = victim UDP to echo (7) or chargen (19) 1 spoofed packet dst = the .255 broadcast Broadcast segment every host runs echo / chargen host replies to victim host replies to victim host replies to victim host replies to victim one packet fans out to many combined reply flood Victim flooded by replies it never asked for A test confirms routers drop directed broadcasts and that echo and chargen are disabled before the fan-out can form. BlackNeuron™
Fraggle attack: one spoofed UDP packet to a broadcast address makes every echo or chargen host on the segment reply to the victim

Why it matters in DDoS testing

Fraggle is a classic that survives only where directed broadcasts and legacy diagnostic services are still enabled. Testing confirms that routers drop directed broadcasts (the no ip directed-broadcast default), that echo and chargen are disabled internally, and that ingress filtering blocks the spoofed sources before they leave the edge. The reflection mechanics shared across these vectors are detailed in Understanding DDoS Attack Vectors.