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Stealthy and multifunctional Linux malware that has been infecting telecommunications companies went largely unnoticed for two years until being documented for the first time by researchers on Thursday.

Researchers from security firm Group-IB have named the remote access trojan “Krasue,” after a nocturnal spirit depicted in Southeast Asian folklore “floating in mid-air, with no torso, just her intestines hanging from below her chin.” The researchers chose the name because evidence to date shows it almost exclusively targets victims in Thailand and “poses a severe risk to critical systems and sensitive data given that it is able to grant attackers remote access to the targeted network.

According to the researchers:

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If your organization uses servers that are equipped with baseboard management controllers from Supermicro, it’s time, once again, to patch seven high-severity vulnerabilities that attackers could exploit to gain control of them. And sorry, but the fixes must be installed manually.

Typically abbreviated as BMCs, baseboard management controllers are small chips that are soldered onto the motherboard of servers inside data centers. Administrators rely on these powerful controllers for various remote management capabilities, including installing updates, monitoring temperatures and setting fan speeds accordingly, and reflashing the UEFI system firmware that allows servers to load their operating systems during reboots. BMCs provide these capabilities and more, even when the servers they’re connected to are turned off.

Code execution inside the BMC? Yup

The potential for vulnerabilities in BMCs to be exploited and used to take control of servers hasn’t been lost on hackers. In 2021, hackers exploited a vulnerability in BMCs from HP Enterprise and installed a custom rootkit, researchers from Amnpardaz, a security firm in Iran, reported that year. ILObleed, as the researchers named the rootkit, hid inside the iLO, a module in HPE BMCs that’s short for Integrated Lights-Out.

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In July, security researchers revealed a sobering discovery: hundreds of pieces of malware used by multiple hacker groups to infect Windows devices had been digitally signed and validated as safe by Microsoft itself. On Tuesday, a different set of researchers made a similarly solemn announcement: Microsoft’s digital keys had been hijacked to sign yet more malware for use by a previously unknown threat actor in a supply-chain attack that infected roughly 100 carefully selected victims.

The malware, researchers from Symantec’s Threat Hunter Team reported , was digitally signed with a certificate for use in what is alternatively known as the Microsoft Windows Hardware Developer Program and the Microsoft Windows Hardware Compatibility Program . The program is used to certify that device drivers—the software that runs deep inside the Windows kernel—come from a known source and that they can be trusted to securely access the deepest and most sensitive recesses of the operating system. Without the certification, drivers are ineligible to run on Windows.

Hijacking keys to the kingdom

Somehow, members of this hacking team—which Symantec is calling Carderbee—managed to get Microsoft to digitally sign a type of malware known as a rootkit. Once installed, rootkits become what’s essentially an extension of the OS itself. To gain that level of access without tipping off end-point security systems and other defenses, the Carderbee hackers first needed its rootkit to receive the Microsoft seal of approval, which it got after Microsoft signed it.

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Hiding malicious programs in a computer’s UEFI firmware, the deep-seated code that tells a PC how to load its operating system, has become an insidious trick in the toolkit of stealthy hackers. But when a motherboard manufacturer installs its own hidden backdoor in the firmware of millions of computers—and doesn’t even put a proper lock on that hidden back entrance—they’re practically doing hackers’ work for them.

Researchers at firmware-focused cybersecurity company Eclypsium revealed today that they’ve discovered a hidden mechanism in the firmware of motherboards sold by the Taiwanese manufacturer Gigabyte, whose components are commonly used in gaming PCs and other high-performance computers. Whenever a computer with the affected Gigabyte motherboard restarts, Eclypsium found, code within the motherboard’s firmware invisibly initiates an updater program that runs on the computer and in turn downloads and executes another piece of software.

While Eclypsium says the hidden code is meant to be an innocuous tool to keep the motherboard’s firmware updated, researchers found that it’s implemented insecurely, potentially allowing the mechanism to be hijacked and used to install malware instead of Gigabyte’s intended program. And because the updater program is triggered from the computer’s firmware, outside its operating system, it’s tough for users to remove or even discover.

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Researchers have unearthed a discovery that doesn’t occur all that often in the realm of malware: a mature, never-before-seen Linux backdoor that uses novel evasion techniques to conceal its presence on infected servers, in some cases even with a forensic investigation.

On Thursday, researchers from Intezer and The BlackBerry Threat Research & Intelligence Team said that the previously undetected backdoor combines high levels of access with the ability to scrub any sign of infection from the file system, system processes, and network traffic. Dubbed Symbiote, it targets financial institutions in Brazil and was first detected in November.

Researchers for Intezer and BlackBerry wrote: