Chaos Malware Resurfaces With All-New DDoS & Cryptomining Modules

The powerful Chaos malware has evolved yet again, morphing into a new Go-based, multiplatform threat that bears no resemblance to its previous ransomware iteration. It's now targeting known security vulnerabilities to launch distributed denial-of-service (DDoS) attacks and perform cryptomining.

Researchers from Black Lotus Labs, the threat intelligence arm of Lumen Technologies, recently observed a version of Chaos written in Chinese, leveraging China-based infrastructure, and exhibiting behavior far different than the last activity seen by the ransomware-builder of the same name, they said in a blog post published Sept. 28.

Indeed, the distinctions between earlier variants of Chaos and the 100 distinct and recent Chaos clusters that researchers observed are so different that they say it poses a brand-new threat. In fact, researchers believe the latest variant is actually the evolution of the DDoS botnet Kaiji and perhaps "distinct from the Chaos ransomware builder" previously seen in the wild, they said.

Kaiji, discovered in 2020, originally targeted Linux-based AMD and i386 servers by leveraging SSH brute-forcing to infect new bots and then launch DDoS attacks. Chaos has evolved Kaiji's original capabilities to include modules for new architectures — including Windows — as well as adding new propagation modules through CVE exploitation and SSH key harvesting, the researchers said.

Recent Chaos Activity

In recent activity, Chaos successfully compromised a GitLab server and unfurled a flurry of DDoS attacks targeting the gaming, financial services and technology, and media and entertainment industries, along with DDoS-as-a-service providers and a cryptocurrency exchange.

Chaos is now targeting not only enterprise and large organizations but also "devices and systems that aren't routinely monitored as part of an enterprise security model, such as SOHO routers and FreeBSD OS," the researchers said.

And while the last time Chaos was spotted in the wild it was acting more as typical ransomware that entered networks with the purpose of encrypting files, the actors behind the latest variant have very different motives in mind, the researchers said.

Its cross-platform and device functionality as well as the stealth profile of the network infrastructure behind the latest Chaos activity appears to demonstrate that the aim of the campaign is to cultivate a network of infected devices to leverage for initial access, DDoS attacks, and cryptomining, according to the researchers.

Key Differences, and One Similarity

While previous samples of Chaos were written in .NET, the latest malware is written in Go, which is rapidly becoming a language of choice for threat actors due to its cross-platform flexibility, low antivirus detection rates, and difficulty to reverse-engineer, the researchers said.

And indeed, one of the reasons that the latest version of Chaos is so powerful is because it operates across multiple platforms, including not only Windows and Linux operating systems but also ARM, Intel (i386), MIPS, and PowerPC, they said.

It also propagates in a far different way than previous versions of the malware. While researchers were unable to ascertain its initial access vector, once it takes hold of a system, the latest Chaos variants exploit known vulnerabilities in a way that shows the ability to pivot quickly, the researchers noted.

"Among the samples we analyzed were reported CVEs for Huawei (CVE-2017-17215) and Zyxel (CVE-2022-30525) personal firewalls, both of which leveraged unauthenticated remote command line injection vulnerabilities," they observed in their post. "However, the CVE file appears trivial for the actor to update, and we assess it is highly likely the actor leverages other CVEs."

Chaos has indeed gone through numerous incarnations since it first emerged in June 2021 and this latest version is not likely to be its last, the researchers said. Its first iteration, Chaos Builder 1.0-3.0, purported to be a builder for a .NET version of the Ryuk ransomware, but the researchers soon noticed it bore little resemblance to Ryuk and was actually a wiper.

The malware evolved across several versions until version four of the Chaos builder that was released in late 2021 and got a boost when a threat group named Onyx created its own ransomware. This version quickly became the most common Chaos edition directly observed in the wild, encrypting some files but maintain overwritten and destroying most of the files in its path.

Earlier this year in May, the Chaos builder traded its wiper capabilities for encryption, surfacing with a rebranded binary dubbed Yashma that incorporated fully fledged ransomware capabilities.

While the most recent evolution of Chaos witnessed by Black Lotus Labs is far different, it does have one significant similarity with its predecessors — rapid growth that is unlikely to slow anytime soon, the researchers said.

The earliest certificate of the latest Chaos variant was generated on April 16; this is subsequently when researchers believe threat actors launched the new variant in the wild.

Since then, the number of Chaos self-signed certificates has shown "marked growth," more than doubling in May to 39 and then jumping to 93 for the month of August, the researchers said. As of Sept. 20, the current month has already surpassed the previous month's total with the generation of 94 Chaos certificates, they said.

Mitigating Risk Across the Board

Because Chaos is now attacking victims from the smallest home offices to the largest enterprises, researchers made specific recommendations for each type of target.

For those defending networks, they advised that network administrators stay on top of patch management for newly discovered vulnerabilities, as this is a principal way Chaos spreads.

"Use the IoCs outlined in this report to monitor for a Chaos infection, as well as connections to any suspicious infrastructure," the researchers recommended.

Consumers with small office and home office routers should follow best practices of regularly rebooting routers and installing security updates and patches, as well as leveraging properly configured and updated EDR solutions on hosts. These users also should regularly patch software by applying vendors' updates where applicable.

Remote workers — an attack surface that has significantly increased over the last two years of the pandemic — also are at risk, and should mitigate it by changing default passwords and disabling remote root access on machines that don't require it, the researchers recommended. Such workers also should store SSH keys securely and only on devices that require them.

For all businesses, Black Lotus Labs recommends considering the application of comprehensive secure access service edge (SASE) and DDoS mitigation protections to bolster their overall security postures and enable robust detection on network-based communications.