New ‘Hildegard’ Malware Targets Kubernetes Systems

The hacking group referred to as TeamTNT has been employing a new piece of malware in a recently started campaign targeting Kubernetes environments, security researchers with Palo Alto Networks’ Unit 42 reveal.

During the summer of 2020, TeamTNT was targeting Docker and Kubernetes systems with a crypto-mining worm capable of stealing local credentials, including Amazon Web Services (AWS) login details.

In a different campaign that was detailed in September 2020, the threat actor was employing a legitimate open source tool named Weave Scope to fingerprint targeted cloud environments and execute commands.

In a brand new campaign that started in January 2021, but which appears to be only in its early stages, the hacking group has targeted Kubernetes environments with a piece of malware called Hildegard, which is both stealthy and persistent.

The malware establishes a connection with its command and control (C&C) server via a tmate reverse shell and an Internet Relay Chat (IRC) channel, disguises the malicious process using the bioset Linux process, hides malicious processes using library injection, and encrypts the malicious payload to hinder analysis.

As part of the observed attacks, once the Kubernetes cluster was compromised, the hackers attempted to spread to additional containers, with the final purpose of the attacks being cryptojacking. However, no new activity has been identified since the initial detection.

The campaign employs tools and domains observed in previous TeamTNT attacks, but the code base and infrastructure appear incomplete, suggesting that the campaign is still under development. Most of the infrastructure is only one month old and some scripts are being frequently updated.

“Knowing this malware’s capabilities and target environments, we have good reason to believe that the group will soon launch a larger-scale attack,” Palo Alto Networks’ researchers say.

In addition to abusing the processing power of Kubernetes clusters for cryptojacking, the malware might also be leveraged for the exfiltration of sensitive data from the applications running in the targeted environments.

Leveraging the reverse shell, the attackers can also manually perform additional reconnaissance and operations.

The Hildegard malware gathers various types of information on the host and also searches for credentials on the host, including cloud access keys and tokens, SSH keys, Docker credentials, and Kubernetes service tokens. All credentials files discovered are sent to the C&C.

“This new TeamTNT malware campaign is one of the most complicated attacks targeting Kubernetes. This is also the most feature-rich malware we have seen from TeamTNT so far. In particular, the threat actor has developed more sophisticated tactics for initial access, execution, defense evasion and C&C,” Palo Alto Networks concludes.

In an emailed comment to SecurityWeek, Tal Morgenstern, co-founder and CPO at vulnerability management firm Vulcan Cyber, pointed out the importance of ensuring that all assets are properly secured, given the nature of this attack.

“In this complex attack, threat actors are leveraging a combination of Kubernetes misconfigurations and known vulnerabilities. DevOps and IT teams must closely coordinate with their counterparts in security to prioritize remediation especially for external-facing assets and high-risk vulnerabilities. It is very possible to quickly secure Kubernetes. The remedies are available, but it takes work, focus and cross-team collaboration to get fix done and prevent these kinds of attacks,” Morgenstern said.

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