The Kimsuky advanced persistent threat (APT) group, linked to North Korea‘s Reconnaissance General Bureau (RGB), has been observed deploying a Linux version of its GoBear backdoor in a campaign targeting South Korean organizations. This backdoor, named Gomir, is structurally similar to GoBear, with extensive code sharing between the two variants. Symantec’s Threat Hunter Team noted that any functionality in GoBear that is operating system-dependent has been either omitted or reimplemented in Gomir.
GoBear was first documented by South Korean security firm S2W in early February 2024, associated with a campaign delivering malware called Troll Stealer, also known as TrollAgent. Troll Stealer overlaps with known Kimsuky malware families like AppleSeed and AlphaSeed. AhnLab Security Intelligence Center (ASEC) found that the malware is distributed via trojanized security programs downloaded from a South Korean construction-related association’s website, including nProtect Online Security, NX_PRNMAN, TrustPKI, UbiReport, and WIZVERA VeraPort.
Symantec also observed Troll Stealer malware being delivered via rogue installers for Wizvera VeraPort, though the exact distribution mechanism remains unknown. GoBear, which supports executing commands from a remote server, shares similar function names with an older Springtail backdoor known as BetaSeed, suggesting a common origin. The malware can be propagated through droppers that pose as fake installers for an app for a Korean transport organization.
Gomir, the Linux counterpart, supports 17 commands, allowing operators to perform file operations, start a reverse proxy, pause command-and-control (C2) communications, run shell commands, and terminate its own process. Symantec emphasized that this latest Springtail campaign indicates that software installation packages and updates are now favored infection vectors for North Korean espionage actors. The targeted software appears carefully chosen to maximize infection chances among South Korean targets.
