A North Korea-linked cyber-espionage group has been noticed leveraging job-themed phishing lures to focus on potential victims in power and aerospace verticals and infect them with a beforehand undocumented backdoor dubbed MISTPEN.
The exercise cluster is being tracked by Google-owned Mandiant below the moniker UNC2970, which it mentioned overlaps with a risk group often known as TEMP.Hermit, which can also be broadly known as Lazarus Group or Diamond Sleet (previously Zinc).
The risk actor has a historical past of focusing on authorities, protection, telecommunications, and monetary establishments worldwide since at the very least 2013 to gather strategic intelligence that furthers North Korean pursuits. It is affiliated with the Reconnaissance Normal Bureau (RGB).
The risk intelligence agency mentioned it has noticed UNC2970 singling out varied entities situated within the U.S., the U.Ok., the Netherlands, Cyprus, Sweden, Germany, Singapore, Hong Kong, and Australia.
“UNC2970 targets victims under the guise of job openings, masquerading as a recruiter for prominent companies,” it mentioned in a brand new evaluation, including it copies and modifies job descriptions in response to their goal profiles.
“Moreover, the chosen job descriptions target senior-/manager-level employees. This suggests the threat actor aims to gain access to sensitive and confidential information that is typically restricted to higher-level employees.”
The assault chains, also called Operation Dream Job, entail the usage of spear-phishing lures to interact with victims over e mail and WhatsApp in an try to construct belief, earlier than sending throughout a malicious ZIP archive file that is dressed up as a job description.
In an fascinating twist, the PDF file of the outline can solely be opened with a trojanized model of a authentic PDF reader utility known as Sumatra PDF included throughout the archive to ship MISTPEN via a launcher known as BURNBOOK.
It is price noting that this doesn’t suggest a provide chain assault neither is there a vulnerability within the software program. Somewhat the assault has been discovered to make use of an older Sumatra PDF model that has been repurposed to activate the an infection chain.
It is a tried-and-tested methodology adopted by the hacking group way back to 2022, with each Mandiant and Microsoft highlighting the usage of a variety of open-source software program, together with PuTTY, KiTTY, TightVNC, Sumatra PDF Reader, and muPDF/Subliminal Recording software program installer for these assaults.
It is believed that the risk actors possible instruct the victims to open the PDF file utilizing the enclosed weaponized PDF viewer program to set off the execution of a malicious DLL file, a C/C++ launcher known as BURNBOOK.
“This file is a dropper for an embedded DLL, ‘wtsapi32.dll,’ which is tracked as TEARPAGE and used to execute the MISTPEN backdoor after the system is rebooted,” Mandiant researchers mentioned. “MISTPEN is a trojanized version of a legitimate Notepad++ plugin, binhex.dll, which contains a backdoor.”
TEARPAGE, a loader embedded inside BURNBOOK, is liable for decrypting and launching MISTPEN. A light-weight implant written in C, MISTPEN is supplied to obtain and execute Transportable Executable (PE) information retrieved from a command-and-control (C2) server. It communicates over HTTP with the next Microsoft Graph URLs.
Mandiant additionally mentioned it uncovered older BURNBOOK and MISTPEN artifacts, suggesting that they’re being iteratively improved so as to add extra capabilities and permit it to fly below the radar. The early MISTPEN samples have additionally been utilizing compromised WordPress web sites as C2 domains.
“The threat actor has improved their malware over time by implementing new features and adding a network connectivity check to hinder the analysis of the samples,” the researchers mentioned.
