Spamhaus has observed a newer type of distributed denial-of-service attack (DDoS) which has only recently become popular among cybercriminals. In just the past month, several attacks using this method have been investigated by private security firms and law enforcement agencies. During December 2011, Spamhaus sustained an SNMP DDoS on the order of magnitude of the largest DDoS seen to date on the Internet. Our anti-DDoS resources allowed us to implement effective measures to mitigate this attack, and we are working with law enforcement and security industry partners to shut down the originators.
This DDoS vector is similar to the older DNS Amplification Attack, but instead of DNS it uses Simple Network Management Protocol (SNMP) services to reflect and amplify a stream of UDP packets toward a DDoS target. The attacker's packets contain forged (spoofed) originating IP addresses, so that the SNMP server to which these packets are sent replies with a large UDP packet to the spoofed address, which belongs to the victim. The amplification effect of this vector can produce high traffic volumes from a relatively small input stream, effectively clogging the 'pipes' into the victim's server to produce denial of service.