New DDoS Attack Method Leverages UPnP

A new DDoS technique is adding a new twist to this common threat and upping the chance that an attack will have an impact on business operations. The new attack leverages a known vulnerability in Universal Plug and Play (UPnP) to get around many of the current defense techniques and swamp a target's network and servers.

The basis of the attack is a DNS amplification technique that bounces a DNS query response to the victim based on a spoofed requester address. In this new DDoS approach, though - detailed by researchers at Imperva - the attack mechanism is a UPnP router that is happy to forward requests from one external source to another (in violation of UPnP behavior rules). Using the UPnP router returns the data on an unexpected UDP port from a spoofed IP address, making it more difficult to take simple action to shut down the traffic flood.

In the original attack and the new proof of concept, a DNS amplification was used, but the researchers note that there's no technical reason that a similar approach couldn't be used in SSDP, DNS, and NTP attacks.

When both source address and port are obfuscated, many current DDoS remediation techniques become ineffective. While deep packet inspection will work against the attack, it's a resource-intensive method that can be both costly and limited. The researchers say that the most effective way to stop this attack method is for organizations to lock down their UPnP routers, taking a weapon out of the hands of attackers.

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