Linux Malware Deemed ‘Nearly Impossible’ to Detect

A new Linux malware that’s “nearly not possible to detect” can harvest qualifications and provides attackers remote obtain and rootkit features by acting in a parasitic way to infect targets, researchers explained.

Researchers from The BlackBerry Exploration and Intelligence Group have been tracking the malware, the earliest detection of which is from November 2021, security researcher Joakim Kennedy wrote in a website put up on the BlackBerry Risk Vector Blog revealed last week.

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Scientists have properly dubbed the malware—which apparently was penned to goal the fiscal sector in Latin America—”Symbiote.” In biology, the word indicates an organism that life in symbiosis with an additional organism.

The name is an homage to how the malware operates, which is differently than other Linux malware that researchers have encountered, Kennedy explained.

“What will make Symbiote distinct … is that it demands to infect other managing procedures to inflict problems on contaminated devices,” he wrote. “Instead of becoming a standalone executable file that is run to infect a device, it is a shared item (SO) library that is loaded into all managing processes utilizing LD_PRELOAD (T1574.006), and parasitically infects the equipment.”

As soon as Symbiote has contaminated all the jogging procedures, a threat actor can engage in numerous nefarious activity, which includes rootkit operation, the skill to harvest credentials, and distant accessibility capability, Kennedy explained.

In addition to the rootkit capacity, the malware also gives a backdoor for the danger actor to log in as any user on the device with a hardcoded password, and to execute commands with the optimum privileges, he extra.

Evasive Maneuvers

Symbiote’s behavior isn’t the only thing that will make it special, researchers mentioned. It’s also extremely evasive to this kind of a diploma that it is “likely to fly underneath the radar,” earning it very hard to know if it’s even staying made use of by risk actors at all, he stated.

Some evasive practices it utilizes is that by design, it is loaded by the linker by using the LD_PRELOAD directive, which lets it to be loaded before any other shared objects, scientists identified. This privilege of remaining loaded to start with will allow it to hijack the imports from the other library files loaded for the software, they said. In this way, it disguise its existence on the equipment by hooking libc and libpcap capabilities, Kennedy explained.

“Once the malware has contaminated a device, it hides alone and any other malware applied by the menace actor, building bacterial infections extremely challenging to detect,” he discussed. “Performing are living forensics on an contaminated equipment may perhaps not flip something up due to the fact all the file, procedures, and network artifacts are hidden by the malware.”

In actuality, scientists claimed they themselves could not uncover adequate evidence to ascertain whether menace actors are now employing Symbiote ” in hugely specific or wide attacks,” he said.

Unconventional DNS requests may be just one way to detect if the malware is present on a process, researchers famous. On the other hand, common antivirus or other security tools aimed at endpoint detection and response won’t select up Symbiote, creating businesses utilizing Linux that rely on those people protections at risk, they mentioned.

Objectives

Attackers’ critical aims for wielding Symbiote are “to seize qualifications and to facilitate backdoor accessibility to infected machines,” Kennedy mentioned. He outlined in detail how the malware achieves both of these pursuits.

For credential harvesting, Symbiote hooks the libc read perform if an ssh or scp procedure is contacting the operate, it captures the credentials, which are to start with encrypted with RC4 working with an embedded essential and then prepared to a file, Kennedy explained.

Attackers not only steal the credentials regionally for entry but also exfiltrate them by hex encoding and chunking up the details to be sent by way of DNS deal with history requests to a domain title that they manage, he included.

To get distant access to an infected device, the malware hooks a couple of Linux Pluggable Authentication Module (PAM) capabilities, which allows it to authenticate to the device with any company that takes advantage of PAM—including distant products and services such as Protected Shell (SSH), Kennedy said.

“When a services tries to use PAM to authenticate a user, the malware checks the furnished password in opposition to a hardcoded password,” he defined. ” If the password provided is a match, the hooked perform returns a achievement response.”

Once the menace actor has achieved authentication, Symbiote lets for an attacker to get root privileges by scanning the setting for the variable HTTP_SETTHIS, Kennedy said.

“If the variable is set with articles, the malware variations the productive consumer and group ID to the root user, and then clears the variable before executing the information by way of the technique command,” he discussed.