New ‘Kaiji’ Botnet Attacks Linux, IoT Devices via SSH Brute Force

Designed to Launch DDoS Attacks, the Golang-Based ‘Kaiji’ Botnet Infects Devices via SSH Brute Force

A recently identified botnet built using the Golang programming language is targeting Linux systems, including Internet of Things (IoT) devices, using a custom implant, Intezer reports.

The botnet, which security researcher MalwareMustDie named Kaiji, is of Chinese origin and spreads exclusively via SSH brute force attacks, targeting the root user only. Designed to launch distributed denial of service (DDoS) attacks, the malware requires root access to craft custom network packets and operate unhindered. 

Kaiji, Intezer explains, was designed to launch a multitude of DDoS attack types, including ipspoof and synack assaults, but also includes a SSH bruteforcer module to spread, and a second SSH spreader to hijack local SSH keys and infect hosts that the server connected to in the past.

Once executed, the malware copies itself to /tmp/seeintlog and launches a second instance to start the malicious operations. Each of these operations is implemented within its own goroutine, and Intezer’s security researchers have identified a total of 13 central goroutines. 

Supported operations include connecting to a command and control (C&C) server, fetching commands from the C&C (DDoS and SSH bruteforce instructions, run shell command, or delete itself), connecting to known hosts, installing persistence, checking CPU usage, or copying the rootkit to /etc/32679 and run it every 30 seconds.

The security researchers discovered that the rootkit tends to invoke itself too many times, consuming the machine’s memory. Together with the fact that the C&C was operational for a short period of time, this suggests that the malware is under development and still in testing, the researchers say. 

To launch DDoS attacks, the malware retrieves both a target and an attack technique from the C&C. Supported assault methods include two TCPFlood implementations (one with raw sockets), two UDPFlood implementations (one with raw sockets), and IPSpoof, SYNACK, SYN, and ACK attacks

“It is rare to see a botnet written from scratch, considering the tools readily available to attackers in blackmarket forums and open source projects. [Kaiji] is another confirmation of an interesting trajectory noted by vendors such as Palo Alto that malware developers are turning to modern languages such as Golang for their operations,” Intezer concludes. 

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