So-called “fileless” malware is infecting Mac OS machines by hiding in memory and never touching files or drives. The malware, masquerading as a piece of crypto trading software called UnionCryptoTrader.dmg, is suspected to be the work of the North Korean hacking group, Lazurus APT.

The malware infects Mac OS computers by injecting an executable file into the boot process, thereby hiding it from the user and rendering it difficult to remove. The executable then looks for various online payloads and runs them in memory, ensuring that anti-virus software could miss the malware after reboots and other OS events. Ultimately, there is very little for an anti-virus app to find as the payload changes over time and the malware has root privileges on infected machines.

The malware is based on AppleJeus by the Lazarus APT Group, a North Korean hacking outfit, and comes from a lineage of fileless Windows and Mac OS Trojans that masquerade as crypto trading apps.

The attackers created a legitimate-sounding crypto trading website called JMTTrading that offered a “smart cryptocurrency arbitrage trading platform.” The website is currently live but doesn’t seem to be delivering its malware payload anymore.

Image via CoinDesk

“It seems reasonable to assume that Lazarus Group is sticking with its successful attack vector (of targeting employees of crypto-currency exchanges with trojanized trading applications) …for now!” wrote Patrick Wardle on security site Objective-See.

According to security research service VirusTotal, only 19 of 72 Mac OS anti-virus apps can detect the malware.

The U.S. Treasury Department previously sanctioned North Korean hacking groups for attempting to steal cryptocurrencies via malware in an effort to pay for military equipment.

“Treasury is taking action against North Korean hacking groups that have been perpetrating cyber attacks to support illicit weapon and missile programs,” said Sigal Mandelker, Treasury Under Secretary for Terrorism and Financial Intelligence in September. “We will continue to enforce existing U.S. and UN sanctions against North Korea and work with the international community to improve cybersecurity of financial networks.”

As reporter Dan Goodin notes, the malware will bring up multiple password requests before it infects your computer, ensuring that only users most in need of fake crypto software will be infected which is obviously cold comfort for those who clicked through and installed the new Trojan.