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NimDoor

Also known asnimdoor

NimDoor is a DPRK-linked macOS malware family and backdoor used by North Korean state-sponsored threat actors in campaigns targeting Web3 and cryptocurrency organizations. Reported targeting includes Web3 startups, crypto-related businesses, and crypto platforms. SentinelLABS grouped the malware family under the name NimDoor, and related reporting cited similar attack chains attributed to DPRK actors. The observed intrusion chain used social engineering via Telegram and Calendly, followed by delivery of a fake Zoom SDK update AppleScript from Zoom-themed spoofed infrastructure. The campaign used a mix of AppleScript, Bash, C++, and Nim components. One execution path deployed a C++ loader that decrypted embedded binaries, spawned a benign-looking target process in a suspended state, and injected a payload using macOS process injection via posix_spawn with POSIX_SPAWN_START_SUSPENDED and SIGCONT. The injected payload communicated with command-and-control over WSS and supported command execution, directory changes, working-directory discovery, and system information collection. It also downloaded Bash scripts that stole data from Arc, Brave, Firefox, Google Chrome, and Microsoft Edge, as well as Keychain material, shell history, and Telegram local encrypted database data, with exfiltration to attacker-controlled infrastructure. A second execution chain used Nim-based binaries including installer, GoogIe LLC, and CoreKitAgent. These components established persistence through a LaunchAgent and hidden configuration files under /private/tmp and user library paths. CoreKitAgent used macOS kqueue and asynchronous Nim execution, included a 10-minute sleep assessed as likely anti-VM or sandbox evasion, and overrode SIGINT and SIGTERM so that termination attempts triggered persistence deployment. CoreKitAgent also decoded and launched an AppleScript backdoor that beaconed every 30 seconds to randomly selected C2 domains and executed server responses via run script. The campaign demonstrates DPRK operators using Nim and other less familiar languages to complicate macOS malware analysis and improve stealth. Known aliases directly reflected in the content: NimDoor.

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OPERATIONAL PROFILE

Targeting

Who, where, and (when attributed) which flag flies behind the operation. Pulled from open-source reporting and Mallory's analyst review.

Who they target

Sectors the actor has been observed targeting.

  • Software & Services
  • Financial Services

Where they're from

Attributed origin per open-source reporting.

  • KP
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Tradecraft mapping

Every observed MITRE ATT&CK technique, grouped by tactic.

Malware arsenal

Families this actor is known to deploy, with IOCs and behavior.

Exploited CVEs

CVEs this actor has used in known campaigns.

Detection signatures

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Observables

Domains, IPs, and hashes tied to this actor, refreshed continuously.