ESET is actively monitoring malicious codes that target IoT systems such as routers, gateways and wireless access points, rather than computers or smartphones.
Security researchers from ESET have discovered a new threat dubbed KTN-RM or Remaiten that targets Internet of Things devices by combining the capabilities of Linux malware known as Tsunami and Gafgyt.
Tsunami is a downloader/IRC Bot backdoor used in the criminal ecosystem to launch DDoS attacks, meanwhile Linux/Gafgyt serves as a backdoor that could be controlled remotely and used as a Telnet scanning.
“Recently, we discovered a bot that combines the capabilities ofTsunami (also known as Kaiten) and Gafgyt. It also provides some improvements as well as a couple of new features. We call this new threat Linux/Remaiten. So far, we have seen three versions ofLinux/Remaiten that identify themselves as versions 2.0, 2.1 and 2.2. Based on artifacts found in the code, the authors call this new malware “KTN-Remastered” or “KTN-RM”.” states the official blog post published by the company.
The KTN-RM malware (aka Remaiten) implements an effective ,’ features an improved spreading mechanism by carrying downloader executable binaries for embedded platforms and other connected devices.
The attack scenario is similar to the one seen in the wild for other IoT threats, the Remaiten malware scan the Internet searching IoT devices that accept Telnet connections, then it tries to connect them by using a dictionary of login credentials. If the malware successfully login the device, it establishes a shell command to download other malicious binaries on the infected system.
The Linux Remaiten downloaders are small ELF executables embedded in the bot binary itself that are executed on the target devices to instruct it in connecting the bot’s C&C server. The researchers at ESET discovered that bot binaries include a hardcoded list of C&C server IP addresses, the bot also sends to the control server information on the infected device (i.e. IP address, login credentials, infection status).
“When instructed to perform telnet scanning, it tries to connect to random IP addresses reachable from the Internet on port 23. If the connection succeeds, it will try to guess the login credentials from an embedded list of username/password combinations. If it successfully logs in, it issues a shell command to download bot executables for multiple architectures and tries to run them. This is a simple albeit noisy way of infecting new victims, as it is likely one of the binaries will execute on the running architecture.” state the post.
The researcher also revealed a curiosity on the malware, the C&C server used for version 2.0 displays a welcome message that references the MalwareMustDie blog, let’s consider it a sort of revenge of the author for the popular team of researchers.