Hack the Route Start free Open app Denial of service
IP source spoofing
Putting a false source address on a packet, the basis of floods and reflection attacks.
Nothing in IP proves a packet's source address, so an attacker can forge it: to hide, to deflect blame, or to make a reflected answer land on a victim. Connectionless protocols (UDP, a lone TCP SYN) are the easy marks, since no return handshake is needed. The network-wide defence is ingress filtering (BCP 38): a provider drops packets whose source could not legitimately come from that customer, and uRPF does the same by checking a source against the routing table. Spoofing underlies SYN floods and DNS amplification alike.