New 'HEH' Botnet Targets Exposed Telnet Services

A potentially destructive peer-to-peer (P2P) botnet has surfaced and is targeting a broad variety of Internet of Things (IoT) devices with exposed or weakly protected telnet services.

Researchers at China-based 360NetLab, who recently discovered the so-called HEH botnet this week, described the malware as capable of wiping all data from infected systems. According to the security vendor, the botnet poses a threat to any device with an exposed telnet service regardless of whether the device is based on x86, ARM, MIPS, PPC, or any other chip architecture.

The malware has been observed spreading via brute-force attacks against servers, routers, and other Internet-connected systems with exposed SSH ports 23 and 2323. The bot — like a growing number of malware tools — is written in GO code. It uses a proprietary P2P protocol to communicate with other infected devices and receive commands. The malware packs three separate components: a P2P module, a module for propagation, and a local HTTP service.

The bot samples 360NetLab analyzed were downloaded and executed via a malicious Shell script. The malicious code does not make any attempt to enumerate the environment it is on. Instead, it just downloads and executes malicious programs for a variety of different CPU architectures one after the other, 360NetLab said. The script and binaries the security vendor analyzed were hosted on a legitimate but likely compromised website.

Once started, the malware kills off multiple services on the infected device depending on the port (23 or 2323) that was used to gain access. Then it starts an HTTP server that initially pulls up a copy of the "Universal Declaration of Human Rights" in Chinese and seven other languages. This initial content is quickly overwritten with data pulled from another infected peer on the botnet, 360NetLab said.

According to the vendor, a self-destruct function in the malware is especially noteworthy. "When the Bot receives a [command] with code number 8, the Bot will try to wipe out everything on all the disks" through a series of Shell commands," the vendor said.

360NetLab's report did not offer insight into whether the HEH botnet would be used to launch distributed denial-of-service (DDoS) attacks, distribute spam and malware, or for other purposes. For the moment, at least, the botnet's attack function has not been implemented, which suggests the HEH botnet is still in development, the security vendor said.

An Ongoing Trend
The HEH bot is part of a growing number of SSH-targeting malware tools written in the Go programming language that have been observed lately. They represent a shift from older IoT malware like Mirai that were developed C or other programming languages like Perl and C++. This year alone, multiple vendors and researchers have reported IoT bots written in Go, including Kaiji, IRCflu, and more recently FritzFrog, a peer-to-peer botnet that has been actively compromising SSH servers since the beginning of this year.

Craig Young, computer security researcher at Tripwire's vulnerability and exposure research team, says the growing popularity of Go among threat actors in interesting. The HEH botnet is one in a series of Go-language-based botnets that appear to be coming out of a small group of malware developers. It suggests either a new generation of malware authors or a new wave of capabilities.

"Go is a very powerful programming language with a wide library of community supported modules," Young says.

Go enables developers to manipulate very low-level behaviors, he notes.

"Malware authors may leverage this to thwart analysis attempts by using custom variations of compression or encryption algorithms," he says.

While malware developed in Go does not necessarily complicate defenses for organizations, it does require them to update their toolkits in some circumstances, Young noted.

The HEH botnet poses little risk to organizations in its current form. For the moment, the malware has only been observed targeting exposed telnet services, which no responsible organization should have, he says.

"For most organizations, the threat of this botnet at this time is minimal, but it could certainly evolve," Young says. "An update to the malware can be pushed out at any moment to introduce new attack and propagation techniques."