A new and previously undocumented Linux threat has emerged, targeting software developers in a way that could put entire supply chains at risk.

Named Quasar Linux, or QLNX, this malware operates as a full-featured remote access trojan built specifically for Linux systems. It combines stealth techniques with targeted credential theft, making it one of the more dangerous Linux implants seen in recent years.

The attack begins long before any obvious sign of infection. QLNX executes entirely in memory, copies itself to a RAM-backed file, and then deletes its own binary from disk, leaving no trace on the hard drive.

The malware disguises its process using names that mimic normal Linux kernel threads, such as [kworker/0:0] or [migration/0], so even a careful administrator would not notice anything unusual.

QLNX internal architecture (Source - Trend Micro) — QLNX internal architecture (Source – Trend Micro)

Researchers from Trend Micro identified and analyzed QLNX after their AI-driven threat hunting platform flagged an unusual Linux implant with notably low detection rates. The team found that the malware carries embedded source code for both its rootkit and PAM backdoor inside the binary itself.

It compiles these components at runtime using the system’s own GCC compiler, then loads them through /etc/ld.so.preload to intercept system-wide activity.

What makes QLNX particularly alarming is its scope. It runs a multi-stage credential harvesting routine that sweeps SSH private keys, browser login databases, cloud configuration files for AWS and Kubernetes, Docker credentials, Git tokens, NPM tokens, PyPI API keys, and any .env files it finds.

All stolen data is sent to the attacker’s command-and-control server over an encrypted connection.

The malware also includes peer-to-peer mesh networking, so each infected system can relay commands to other compromised hosts, making eradication harder.

Organizations are advised to monitor for process names mimicking kernel threads, inspect /etc/ld.so.preload for unexpected entries, audit developer endpoints for suspicious shared library files, and review cloud credential stores after any suspected infection.

QLNX Targets Developers for Supply Chain Access

The most alarming aspect of QLNX is not what it does to a single machine, but what it enables downstream.

Developers are high-value targets because their credentials unlock publishing pipelines for packages used by thousands of users.

By stealing NPM and PyPI authentication tokens, QLNX gives its operator the ability to push malicious packages into trusted registries without raising immediate red flags.

Supply chain attacks through open-source ecosystems like PyPI and npm have become one of the most effective methods available to threat actors today.

Four-step handshake sequence before entering the command loop (Source - Trend Micro) — Four-step handshake sequence before entering the command loop (Source – Trend Micro)

A single compromised maintainer account could be used to trojanize a legitimate package, inject backdoors into build artifacts, or pivot into cloud environments where production infrastructure lives. The damage from one infected developer machine can be enormous.

The malware harvests SSH keys to move laterally to other servers in the user’s known host chain. This means the initial compromise can quietly spread to cloud instances and CI/CD pipelines long before anyone detects a problem.

QLNX’s ability to wipe system logs including auth.log, syslog, and bash_history makes forensic investigation significantly harder after the fact.

Stealth, Persistence, and PAM Backdoor

QLNX goes to exceptional lengths to remain hidden and survive reboots. It registers persistence through systemd services, crontab reboot entries, init.d scripts, and modifications to the user’s .bashrc file. Even if one persistence method is removed, the others ensure the malware restarts automatically, making full eradication genuinely difficult.

The PAM backdoor is one of QLNX’s most technically sophisticated components. PAM, or Pluggable Authentication Module, handles logins on Linux systems. QLNX injects a malicious PAM module that intercepts credentials in plaintext the moment a user authenticates, then stores captured passwords in a hidden log file at /var/log/.ICE-unix using XOR-encrypted logging.

The eBPF-based kernel rootkit hides the malware’s process IDs, file names, and network ports at the kernel level, making standard tools like ps, top, or netstat ineffective.

The combination of in-memory execution, log wiping, and PAM interception creates a threat that is difficult to detect even on monitored systems. Organizations running Linux developer environments should treat this as an urgent concern and review their endpoint visibility practices immediately.

Indicators of Compromise (IoCs):-

Type	Indicator	Description
SHA-256	ea1d34b21b739a6bbf89b3f7e67978005cf7f3eda612cefc7eac1c8ead7c5545	Quasar-implant binary
SHA-256	82DAA93219BA40A6E41CDF3174BA57EB5D3383D1CD805584E9954EB0200182A1	libsecurity_utils.so.1 (LD_PRELOAD rootkit)
SHA-256	42D0C420EB5FE181388F2E4F0B7D7C0D302971E7A06FDC1BEC481B68C8CCAE1F	pam_security.so (PAM backdoor)
SHA-256	C99CF0DC1EF1057D713CB082ACAF42E4DF4656809C91741752BDDCAB39BBFACA	hide_src_39ZoR.cb
SHA-256	CEA89CAAB82181881D971BE312412795051F6322B105C8B9D29CFB5729FAB8D33	pam_src_51yC3.f
SHA-256	F417430b2d4ae8d005224a9ff5dcb4007d452338acbcbcbb62c4e8ed1a70552dd	libpam_cache.so
SHA-256	d55549d5655e2f202e215676f4bdb0994ea08a93d15ec4ded413f64cfa7facc8	pcs_3kf9x.c
MD5	570f707430f28a7ab836d1c659333152ab9a	quasar-implant (MD5)
SHA-1	b0f2c668cbdd63a87c1c090c95b2c6f9c3e9c3111158752e	quasar-implant (SHA-1)
File Path	/usr/lib/libsecurity_utils.so.1	LD_PRELOAD rootkit shared object
File Path	/usr/lib/.libpam_cache.so	PAM credential hook shared object
File Path	/etc/ld.so.preload	Modified to load rootkit and PAM hook
File Path	/tmp/.pam_cache	Plaintext credential log
File Path	/var/log/.Test-unix	Hidden log for captured SSH passwords
File Path	/var/log/.ICE-unix	Hidden log for captured PAM passwords
File Path	/tmp/.X752e2ca1-lock	Single-instance mutex lock file
File Path	~/.config/systemd/user/quasar_linux.service	Systemd user service persistence file
File Path	~/.config/autostart/quasar_linux.desktop	XDG autostart persistence file
File Path	/etc/systemd/system/quasar_linux.service	Systemd system service persistence file
File Path	/etc/init.d/quasar_linux	init.d script persistence file

Note: IP addresses and domains are intentionally defanged (e.g., [.]) to prevent accidental resolution or hyperlinking. Re-fang only within controlled threat intelligence platforms such as MISP, VirusTotal, or your SIEM.

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