The Internet of things movement has given rise to a new era of connected, vulnerable devices that are being assembled to enable a massive distributed denial-of-service (DDoS) attack. Security firm Arbor Networks is reporting that it has discovered a botnet made up of IoT devices attacking institutions in Brazil with up to 400G bps of attack traffic.
The IoT botnet makes use of the LizardStresser DDoS code that is designed to run on Linux. The LizardStresser code was originally developed by the Lizard Squad DDoS hacker group, which in the past has taken credit for attacks against Lenovo, Microsoft's Xbox Live and Sony's PlayStation Network.
There are two parts to LizardStresser—the command and control (C2) server element and the client side, which is what runs on the compromised endpoint device, often referred to as a zombie. There isn't always a direct correlation between the number of C2s and zombies. In the case of the IoT botnet attacking Brazil, Kirk Soluk, threat intelligence and response manager at Arbor Networks, said there were estimated to be several thousand infected IoT devices for a small handful of C2s. It's also not entirely clear if all LizardStresser C2 nodes are under the control of a single threat actor or multiple groups.
"It is not a one-to-one C2 to threat actor relationship or an all-C2-to-one threat actor type of relationship, but rather somewhere in the middle," Soluk told eWEEK. "Given that the source code for LizardStresser was leaked in early 2015, it is most likely a small number of C2s per threat actor."
For the 400G-bps IoT botnet that is attacking Brazil, Arbor Networks' analysis revealed that attackers were able to abuse Telnet ports on vulnerable devices. Telnet use has long been deprecated as a best practice by IT security professionals as it is an unencrypted approach for remote access. Soluk noted that it wouldn't be accurate to state that Telnet is left open on all IoT devices.
"That being said, since IoT devices are largely unattended or not directly interacted with [like a PC], there often needs to be some method for remotely managing the device," he said. "Telnet is a common remote management service built into most IP stacks, making it a convenient, low-cost remote management option."
However, Soluk said that in this case it was the fact that Telnet was left open along with a default username and password that allowed the devices to be so trivially co-opted into the botnet.
From a size perspective, given that IoT devices tend to have smaller compute and bandwidth capabilities, being able to generate a 400G-bps attack could require a different number of compromised devices than a regular server-based botnet would.
As an example, Soluk said that a Raspberry Pi B+, which is a popular small form-factor device, supports 10/100M-bps Ethernet. As such, it would take 4,000 Raspberry Pis generating 100M bps each to achieve a 400G-bps attack. However, 100M bps is a theoretical maximum and does not occur in practice, he added. Assuming a maximum bandwidth of 90M bps, an attacker would need approximately 4,500 Raspberry Pis for a 400G-bps DDoS attack.
"Of course, residential uplinks won't support 90M bps," Soluk said. "Instead, let's assume a more likely uplink speed of 30M bps, which would triple the number of Raspberry Pis needed to 13,500."
Bandwidth available in a DDoS attack depends on a lot of factors, he said, and it's most likely the bandwidth of the network that the device is connected to rather than the device itself that matters most.
From a defender's perspective, there are a couple of simple steps that could help end users keep their IoT devices from become LizardStresser botnet zombies.
"Changing default passwords and positioning the devices behind a firewall to restrict access would have helped in this case," Soluk said.
Sean Michael Kerner is a senior editor at eWEEK and InternetNews.com. Follow him on Twitter @TechJournalist.