Andariel is a threat group that the Korean Financial Security Institute designated as a subgroup of Lazarus, as Kaspersky reported in 2021. AhnLab described it in 2018 as active since 2015 and linked its activity to earlier operations against South Korean organizations. Its targets span military and defense bodies, political organizations, security and technology companies, energy research, banks, cash machines, cryptocurrency exchanges, and other financially relevant businesses. Characteristic access methods include spear-phishing documents with macros, watering holes that exploit locally used ActiveX software, attacks on centralized management products, and supply-chain compromise. By 2018 it was also expanding reconnaissance beyond Internet Explorer, collecting browser and software details from compromised Korean websites. Activity observed from 2020 into 2021 showed further evolution toward staged in-memory loaders, interactive backdoor use, and selectively deployed custom ransomware, combining intelligence collection with direct financial gain.
Rook Ransomware
#Rook • 2026-03
In March 2026, ESET observed Andariel deploy TigerRAT on a host at a South Korean engineering company and attempt to spread Rook ransomware variants across multiple network endpoints — the first Andariel-attributed activity in ESET telemetry in two years. The victim manufactures high-end industrial equipment reportedly used in liquid hydrogen handling (a known rocket fuel) and the nuclear industry, both of clear interest to the DPRK's ballistic and nuclear programs. ESET assesses the primary objective was strategic technology theft, with Rook likely deployed as a secondary component to distract defenders and opportunistically generate revenue to fund operations.
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