“Test files” associated with the XZ Utils backdoor have made their way to a Rust crate known as liblzma-sys, new findings from Phylum reveal.

liblzma-sys, which has been downloaded over 21,000 times to date, provides Rust developers with bindings to the liblzma implementation, an underlying library that is part of the XZ Utils data compression software. The impacted version in question is 0.3.2.

“The current distribution (v0.3.2) on Crates.io contains the test files for XZ that contain the backdoor,” Phylum noted in a GitHub issue raised on April 9, 2024.

“The test files themselves are not included in either the .tar.gz nor the .zip tags here on GitHub and are only present in liblzma-sys_0.3.2.crate that is installed from Crates.io.”

Following responsible disclosure, the files in question (“tests/files/bad-3-corrupt_lzma2.xz” and “tests/files/good-large_compressed.lzma”) have since been removed from liblzma-sys version 0.3.3 released on April 10. The previous version of the crate has been pulled from the registry.

“The malicious tests files were committed upstream, but due to the malicious build instructions not being present in the upstream repository, they were never called or executed,” Snyk said in an advisory of its own.

The backdoor in XZ Utils was discovered in late March when Microsoft engineer Andres Freund identified malicious commits to the command-line utility impacting versions 5.6.0 and 5.6.1 released in February and March 2024, respectively. The popular package is integrated into many Linux distributions.

The code commits, made by a now-suspended GitHub user named JiaT75 (aka Jia Tan), essentially made it possible to circumvent authentication controls within SSH to execute code remotely, potentially allowing the operators to take over the system.

“The overall compromise spanned over two years,” SentinelOne researchers Sarthak Misraa and Antonio Pirozzi said in an analysis published this week. “Under the alias Jia Tan, the actor began contributing to the xz project on October 29, 2021.”

“Initially, the commits were innocuous and minor. However, the actor gradually became a more active contributor to the project, steadily gaining reputation and trust within the community.”

According to Russian cybersecurity company Kaspersky, the trojanized changes take the form of a multi-stage operation.

“The source code of the build infrastructure that generated the final packages was slightly modified (by introducing an additional file build-to-host.m4) to extract the next stage script that was hidden in a test case file (bad-3-corrupt_lzma2.xz),” it said.

“These scripts in turn extracted a malicious binary component from another test case file (good-large_compressed.lzma) that was linked with the legitimate library during the compilation process to be shipped to Linux repositories.”

The payload, a shell script, is responsible for the extraction and the execution of the backdoor, which, in turn, hooks into specific functions – RSA_public_decrypt, EVP_PKEY_set1_RSA, and RSA_get0_key – that will allow it to monitor every SSH connection to the infected machine.

The primary goal of the backdoor slipped into liblzma is to manipulate Secure Shell Daemon (sshd) and monitor for commands sent by an attacker at the start of an SSH session, effectively introducing a way to achieve remote code execution.

While the early discovery of the backdoor averted what could have been a widespread compromise of the Linux ecosystem, the development is once again a sign that open-source package maintainers are being targeted by social engineering campaigns with the goal of staging software supply chain attacks.

In this case, it materialized in the form of a coordinated activity that presumably featured several sockpuppet accounts that orchestrated a pressure campaign aimed at forcing the project’s longtime maintainer to bring on board a co-maintainer to add more features and address issues.

“The flurry of open source code contributions and related pressure campaigns from previously unknown developer accounts suggests that a coordinated social engineering campaign using phony developer accounts was used to sneak malicious code into a widely used open-source project,” ReversingLabs said.

SentinelOne researchers revealed that the subtle code changes made by JiaT75 between versions 5.6.0 and 5.6.1 suggest that the modifications were engineered to enhance the backdoor’s modularity and plant more malware.

As of April 9, 2024, the source code repository associated with XZ Utils has been restored on GitHub, nearly two weeks after it was disabled for a violation of the company’s terms of service.

The attribution of the operation and the intended targets are currently unknown, although in light of the planning and sophistication behind it, the threat actor is suspected to be a state-sponsored entity.

“It’s evident that this backdoor is highly complex and employs sophisticated methods to evade detection,” Kaspersky said.

Apr 10, 2024NewsroomSoftware Security / Vulnerability

A critical security flaw in the Rust standard library could be exploited to target Windows users and stage command injection attacks.

The vulnerability, tracked as CVE-2024-24576, has a CVSS score of 10.0, indicating maximum severity. That said, it only impacts scenarios where batch files are invoked on Windows with untrusted arguments.

“The Rust standard library did not properly escape arguments when invoking batch files (with the bat and cmd extensions) on Windows using the Command API,” the Rust Security Response working group said in an advisory released on April 9, 2024.

“An attacker able to control the arguments passed to the spawned process could execute arbitrary shell commands by bypassing the escaping.”

The flaw impacts all versions of Rust before 1.77.2. Security researcher RyotaK has been credited with discovering and reporting the bug to the CERT Coordination Center (CERT/CC).

RyotaK said the vulnerability – codenamed BatBadBut – impacts several programming languages and that it arises when the “programming language wraps the CreateProcess function [in Windows] and adds the escaping mechanism for the command arguments.”

But in light of the fact that not every programming language has addressed the problem, developers are being recommended to exercise caution when executing commands on Windows.

“To prevent the unexpected execution of batch files, you should consider moving the batch files to a directory that is not included in the PATH environment variable,” RyotaK said in a word of advice to users.

“In this case, the batch files won’t be executed unless the full path is specified, so the unexpected execution of batch files can be prevented.”

Jan 29, 2024NewsroomRansomware / Malware

Cybersecurity researchers have detected in the wild yet another variant of the Phobos ransomware family known as Faust.

Fortinet FortiGuard Labs, which detailed the latest iteration of the ransomware, said it’s being propagated by means of an infection that delivers a Microsoft Excel document (.XLAM) containing a VBA script.

“The attackers utilized the Gitea service to store several files encoded in Base64, each carrying a malicious binary,” security researcher Cara Lin said in a technical report published last week. “When these files are injected into a system’s memory, they initiate a file encryption attack.”

Faust is the latest addition to several ransomware variants from the Phobos family, including Eking, Eight, Elbie, Devos, and 8Base. It’s worth noting that Faust was previously documented by Cisco Talos in November 2023.

The cybersecurity firm described the variant as active since 2022 and “does not target specific industries or regions.”

The attack chain commences with an XLAM document that, when opened, downloads Base64-encoded data from Gitea in order to save a harmless XLSX file, while also stealthily retrieving an executable that masquerades as an updater for the AVG AntiVirus software (“AVG updater.exe”).

The binary, for its part, functions as a downloader to fetch and launch another executable named “SmartScreen Defender Windows.exe” in order to kick-start its encryption process by employing a fileless attack to deploy the malicious shellcode.

“The Faust variant exhibits the ability to maintain persistence in an environment and creates multiple threads for efficient execution,” Lin said.

The development comes as new ransomware families such as Albabat (aka White Bat), Kasseika, Kuiper, Mimus, and NONAME have gained traction, with the former a Rust-based malware that’s distributed in the form of fraudulent software such as a fake Windows 10 digital activation tool and a cheat program for the Counter-Strike 2 game.

Trellix, which examined the Windows, Linux, and macOS versions of Kuiper earlier this month, attributed the Golang-based ransomware to a threat actor named RobinHood, who first advertised it on underground forums in September 2023.

“The concurrency focused nature of Golang benefits the threat actor here, avoiding race conditions and other common problems when dealing with multiple threads, which would have otherwise been a (near) certainty,” security researcher Max Kersten said.

“Another factor that the Kuiper ransomware leverages, which is also a reason for Golang’s increased popularity, are the language’s cross-platform capabilities to create builds for a variety of platforms. This flexibility allows attackers to adapt their code with little effort, especially since the majority of the code base (i.e., encryption-related activity) is pure Golang and requires no rewriting for a different platform.”

NONAME is also noteworthy for the fact that its data leak site imitates that of the LockBit group, raising the possibility that it could either be another LockBit or that it collects leaked databases shared by LockBit on the official leak portal, researcher Rakesh Krishnan pointed out.

The findings follow a report from French cybersecurity company Intrinsec that connected the nascent 3AM (also spelled ThreeAM) ransomware to the Royal/BlackSuit ransomware, which, in turn, emerged following the shutdown of the Conti cybercrime syndicate in May 2022.

The links stem from a “significant overlap” in tactics and communication channels between 3 AM ransomware and the “shared infrastructure of ex-Conti-Ryuk-TrickBot nexus.”

That’s not all. Ransomware actors have been observed once again using TeamViewer as an initial access vector to breach target environments and attempt to deploy encryptors based on the LockBit ransomware builder, which leaked in September 2022.

“Threat actors look for any available means of access to individual endpoints to wreak havoc and possibly extend their reach further into the infrastructure,” cybersecurity firm Huntress said.

In recent weeks, LockBit 3.0 has also been distributed in the form of Microsoft Word files disguised as resumes targeting entities in South Korea, according to the AhnLab Security Intelligence Center (ASEC).