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The attackers simply used the cumulative bandwidth available to the IoT devices they have infected with the LizardStresser malware.
The malware was created by the Lizard Squad DDoS group, which published its source code in early 2015, enabling other aspiring DDoS attackers to build their own botnets.
LizardStresser activity has increased throughout 2016, with IoT devices starting to becoming a frequent target.
Researchers at Arbor Networks believe LizardStresser is targeting IoT devices for four key reasons.
Read more about DDoS attacks
- DDoS attacks have become a commodity, and are available openly on professional services online marketplaces for as little as $5 an hour.
- There is a real concern that many companies are being affected by DDoS attacks commissioned by competitors, according to Kaspersky Lab.
- Smaller DDoS attacks can be more dangerous than a powerful assault that knocks a company offline but does not install malware or steal data, warns Neustar.
- Attackers have discovered new ways to conduct DDoS attacks. Expert Nick Lewis explains how they work, and what enterprises can do about them.
Second, IoT devices are likely have total access to the internet without any bandwidth limitations or filtering.
Third, the stripped-down operating system and processing power in most IoT devices leaves less room for security features, including auditing, and most compromises go unnoticed by the owners.
Finally, to save engineering time, manufacturers of IoT devices sometimes re-use portions of hardware and software in different classes of device. As a result of this software re-use, the default passwords used to manage the device initially may be shared across different classes of device.
The protocol is essentially a lightweight version of the internet relay chat (IRC) protocol, according to Arbor’s Matthew Bing.
Infected clients will connect to the server and receive commands to launch DDoS attacks using a variety of attack methods, he wrote in a blog post.
Clients can run arbitrary shell commands that are useful for downloading updated versions of LizardStresser or entirely different malware.
Clients can also connect to random IP addresses and attempt to log in via telnet using a list of hard-coded usernames and passwords as a propagation method. Successful logins are reported back to the C&C server for later assimilation into the botnet.
The threat actors
Arbor has been tracking two LizardStresser C&C servers that its researchers believe are operated by the same group of threat actors.
“Although they appear to speak English between each other, their prime targets have exhibited interest in Brazil, as well as gaming sites worldwide,” said Bing.
One attack was linked to more than 1,000 source IP addresses and peaked at more than 400Gbps.
The researchers said the attack is interesting because the attack packets do not appear to be spoofed, meaning the traffic originates from the source addresses in the packets without amplification relying on the user datagram protocol (UDP), such as the network time protocol (NTP) or the simple network management protocol (SNMP).
“This was likely the threat actors tuning their attacks for maximum impact. The UDP-based portions of the attack were further characterised as originating from UDP high ports to destination port UDP/443 with a packet size of around1,400 bytes,” he wrote.
Researchers traced most of the attack sources to Vietnam, followed by Brazil, but there were also other sources scattered around the globe.
Almost 90% of the hosts that responded had an HTML title of “NETSurveillance WEB”, said Bing, which appears to be generic code used by a variety of internet-accessible webcams.
A default password for the root user is available online, and telnet is enabled by default, he said. “We believe the threat actors customised the LizardStresser brute-force code to use this published but under-utilised default password for IoT devices based on the NETSurveillance code.”
The publicly available version of LizardStresser generates IP addresses to brute-force randomly, but Bing said it is possible that this attacker modified the code to prefer certain geographic locations. Another possibility, he said, is that Vietnam and Brazil are the major users of IoT devices running NETSurveillance.
LizardStresser is becoming the most popular botnet for IoT devices, the researchers said, because it makes it easy for threat actors to tweak telnet scanning.
With minimal research into default passwords for IoT devices, attackers are able to enlist an exclusive group of victims into their botnets.
Rise of the DDoS attack
But DDoS attacks are also popular as a way for cyber criminals to demonstrate their attack capabilities, mainly for extortion purposes.
Other cyber criminal groups sell DDoS tools that enable business organisations to disrupt the online services of their competitors.
A growing number of businesses are also seeing DDoS attacks being used as a distraction or smokescreen for installing malware and stealing data.
Taken together, these trends mean that virtually no organisation is safe from a DDoS attack. DDoS makes attacks easier to carry out by a range of actors for a variety of motives.