New Linux Backdoor Attacking Linux Users Via Installation Packages

Linux is widely used in numerous servers, cloud infrastructure, and Internet of Things devices, which makes it an attractive target for gaining unauthorized access or spreading malware. 

Besides this, its open-source nature allows threat actors to study the code and identify new vulnerabilities in it closely.

Cybersecurity researchers at Symantec recently identified a new Linux backdoor actively attacking Linux users via installation packages.

New Linux Backdoor

Symantec unveiled a new Linux backdoor named Linux.Gomir, which had been developed by the Springtail hacking group from North Korea has reportedly been connected with recent malware attacks on South Korean targets.

Gomir is similar to the GoBear backdoor, which was found in previous Springtail campaigns where Trojanized software was used.

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Springtail believed to be a tight-knit organization within the North Korean military intelligence, has carried out cyber espionage missions before, including the 2014 disk wiper attack on Korea Hydro and Nuclear Power. 

They recently misused DMARC policies for social engineering purposes, impersonating experts on issues concerning North Korea.

The Springtail group launched a campaign delivering the new Troll Stealer malware, a Go-based information stealer with overlapping code from previous Springtail malware like GoBear or BetaSeed backdoors. 

Troll Stealer was distributed via Trojanized software installers, including those for TrustPKI, NX_PRNMAN from SGA Solutions, and Wizvera VeraPort, which was previously compromised in 2020. 

Targeting government agencies by copying GPKI data, the campaign exploited legitimate websites requiring a login. 

GoBear was also spread, masquerading as a Korean transport org’s app installer with a stolen cert.

Symantec noticed Linux.Gomir, a Linux version of Springtail’s GoBear Windows backdoor, which shares much code similarity.

If run with the “install” argument, Gomir checks its privileges by copying itself to /var/log/syslogd and creating a persistent systemd service if it is root or else configuring a crontab entry.

When installed, it communicates over HTTP POST with its C&C server, sending an infection ID after hashing the hostname and the username and receiving Base64-encoded commands.

Gomir’s structure and installation routines, which are remarkably similar to those of GoBear, also highlight the group’s cross-platform targeting capabilities.

Gomir employs custom encryption to decode received commands, with this ensuring that the system can support 17 GoBear-like operations. 

This campaign reveals North Korean groups’ inclination toward software supply chain vectors such as Trojanized installers, fake apps, and compromised update channels.

Springtail carefully chooses popular software among desired South Korean audiences to Trojanize them on third-party websites where they must be installed.

The group’s developing tactics exhibit a sophisticated and targeted approach to cyber espionage operations.

IOCs

• 30584f13c0a9d0c86562c803de350432d5a0607a06b24481ad4d92cdf7288213 – Linux.Gomir
• 7bd723b5e4f7b3c645ac04e763dfc913060eaf6e136eecc4ee0653ad2056f3a0 – GoBear Dropper
• d7f3ecd8939ae8b170b641448ff12ade2163baad05ca6595547f8794b5ad013b – Troll Stealer
• 36ea1b317b46c55ed01dd860131a7f6a216de71958520d7d558711e13693c9dc – Troll Stealer
• 8e45daace21f135b54c515dbd5cf6e0bd28ae2515b9d724ad2d01a4bf10f93bd – Troll Stealer
• 6c2a8e2bbe4ebf1fb6967a34211281959484032af1d620cbab390e89f739c339 – Troll Stealer
• 47d084e54d15d5d313f09f5b5fcdea0c9273dcddd9a564e154e222343f697822 – Troll Stealer
• 8a80b6bd452547650b3e61b2cc301d525de139a740aac9b0da2150ffac986be4 – Troll Stealer
• 380ec7396cc67cf1134f8e8cda906b67c70aa5c818273b1db758f0757b955d81  – Troll Stealer
• ff945b3565f63cef7bb214a93c623688759ee2805a8c574f00237660b1c4d3fd – Troll Stealer
• cc7a123d08a3558370a32427c8a5d15a4be98fb1b754349d1e0e48f0f4cb6bfc  – Troll Stealer
• 8898b6b3e2b7551edcceffbef2557b99bdf4d99533411cc90390eeb278d11ac8 – Troll Stealer
• ecab00f86a6c3adb5f4d5b16da56e16f8e742adfb82235c505d3976c06c74e20 – Troll Stealer
• d05c50067bd88dae4389e96d7e88b589027f75427104fdb46f8608bbcf89edb4 – Troll Stealer
• a98c017d1b9a18195411d22b44dbe65d5f4a9e181c81ea2168794950dc4cbd3c – Troll Stealer
• 831f27eb18caf672d43a5a80590df130b0d3d9e7d08e333b0f710b95f2cde0e0 – Troll Stealer
• bc4c1c869a03045e0b594a258ec3801369b0dcabac193e90f0a684900e9a582d – Troll Stealer
• 5068ead78c226893df638a188fbe7222b99618b7889759e0725d85497f533e98 – Troll Stealer
• 216.189.159[.]34

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