May 6, 2020 By David Bisson 2 min read

A new Linux malware strain known as “Kaiji” is targeting internet of things (IoT) devices via SSH brute-force attacks.

Intezer came across this piece of Linux malware in April, when the security firm’s researchers observed the botnet targeting IoT devices and servers with SSH brute-force techniques. They also noticed that the threat, dubbed “Kaiji” for one of its function names, differed from other IoT botnets in that it didn’t derive much of its attack functionality from established malware families, such as the open-source Mirai. Instead, those responsible for the malware had written Kaiji entirely from scratch using Golang, a rare programming language for the IoT botnet scene.

Its programming language wasn’t the only thing that distinguished Kaiji from other digital threats. Intezer also witnessed Kaiji using SSH brute-forcing to target the root user specifically. This technique proved important to the malware’s ability to conduct distributed denial-of-service (DDoS) attacks, as some of these types of attacks are possible only with the use of custom network packets that are solely given to a privileged user.

Other IoT Botnets’ Brute-Force Attacks

Kaiji isn’t the only Linux malware that has used brute-force attacks to target IoT devices. Back in January 2020, for instance, Palo Alto Networks’ Unit 42 announced it had uncovered a new variant of the Muhstik botnet that had incorporated a scanner for the purpose of targeting Tomato routers via web authentication brute-forcing.

In March, Unit 42 spotted the Mukashi Mirai variant scanning the TCP port 23 of random hosts, conducting brute-force attacks and reporting a successful authentication attempt to its command-and-control (C&C) server. Most recently in April, Bitdefender shared its findings on dark_nexus, an IoT botnet that had added a large number of brute-force combinations earlier in the spring.

Defend Against IoT Linux Malware

Security professionals can help their organizations defend against IoT Linux malware such as Kaiji by bolstering capabilities to passively discover all of their IoT devices. You can’t help mitigate a malware infection of connected devices if you don’t know about those smart products in the first place.

At that point, security teams should make sure to protect their IoT devices with strong, unique passwords along with multifactor authentication (MFA) wherever possible.

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