North Korea’s Kimsuky Attacks Rivals’ Trusted Platforms

North Korea-linked threat groups are increasingly using living-off-the-land (LotL) techniques and trusted services to evade detection, with a recent Kimsuky campaign showcasing the use of PowerShell scripts and storing data in Dropbox folders, along with improved operational security.

In the campaign, dubbed “DEEP#DRIVE” by security firm Securonix, the threat group used fake work logs, insurance documents, and crypto-related files to convince users to download and run a zipped shortcut file that gathers system configuration information and then executes PowerShell and .NET scripts. The attack tools upload the system data to Dropbox folders and then download additional commands and capabilities for further compromise.

While the attackers showed some interest in quick financial wins — such as targeting cryptocurrency users — for the most part, the threat group focused on stealing sensitive data from South Korean government agencies and businesses, says Tim Peck, a senior threat researcher at Securonix.

“We observed evidence of both espionage and financial motivation, though leaning more toward espionage,” he says. “This aligns with Kimsuky’s historical targeting of South Korean government agencies, enterprises, and strategic industries.”

North Korean cyber-operations groups have consistently targeted South Korea and the US, with South Korean government agencies and companies among the most popular targets. In September 2024, the FBI warned that North Korean groups planned to launch a surge of attacks against organizations with significant cryptocurrency reserves, and Kimsuky launched a similar multistage attack against South Korean targets last year.

A Prolific Group

Kimsuky isn’t monolithic, but has five threat groups that have overlap with what other companies consider to be the same group, says threat intelligence firm Recorded Future. One group tends to focus on the healthcare and hospitality sectors, for example, while another focuses on cryptocurrency markets.

By mid-2023, Kimsuky became the most prolific North Korean group. (More recent data not available.) Source: Recorded Future’s “North Korea’s Cyber Strategy” report

The Kimsuky groups accounted for the most attacks identified as North Korean in origin between 2021 and 2023, according to Recorded Future’s “North Korea Cyber Strategy” report. In 2024, the groups continued to account for a high volume of attacks, says Mitch Haszard, senior threat intelligence analyst with Recorded Future.

“These groups conduct high volume phishing campaigns, primarily targeting individuals and organizations in South Korea, while occasionally targeting entities in other countries,” he says. “In the activity we see, these groups appear to be going for volume, rather than more time-consuming, tailored spear-phishing operations.”

Other well known North Korean groups, such as Lazarus and Andariel, are not as prolific as the Kimsuky threat actors. While some of those groups are more focused on gathering sensitive information, nearly all also have a financial motivation.

Thousands of Victims?

In the DEEP#DRIVE campaign, following the compromise of a system, the Kimsuky group’s attack scripts upload data on the system configuration to one of several Dropbox folders. While the Securonix researchers were not able to gather intelligence from all the suspected Dropbox locations, they uncovered signs of more than 8,000 configuration files, although some appear to be duplicates, Peck says.

While that means they likely came from the same victim organizations, the campaign appears to be quite successful, he says.

“There were two factors which contributed to the ‘uniqueness’ of the configuration file, the username, and IP address,” Peck says. “Some usernames were associated with dozens of similar IP addresses, which could indicate lateral movement by the attacker — [that is], infecting dozens of machines from the same entity.”

The data from a compromised system includes the host IP address, the system uptime, details about the OS type and version, any installed security software, and a list of running processes.

Kimsuky Improves Its OpSec

The campaign also highlighted North Korean cyber-operations groups’ improvements to operational security. The group used OAuth-based authentication on its Dropbox folders, preventing traditional URL-blocking or network-based defenses from following the links. The threat actors also quickly took down components of their infrastructure soon after the Securonix researchers began investigating, Securonix’s Peck says.

“This level of operational awareness is not always present in phishing-driven malware campaigns,” he says.

For companies, the threat group’s tactics underscore that the hidden file extensions should be disabled, shortcut files should be blocked from executing in user folders, and only signed PowerShell scripts be allowed to execute. Those three countermeasures make the attackers’ activity much easier to detect, Peck says.

In addition, companies in targeted industries — such as cryptocurrency exchanges and government agencies — should bolster their email security and regularly train employees on how to spot phishing threats, says Recorded Future’s Haszard.

“Most North Korean cyberattacks still start with social engineering and a phish,” he says. “Companies should ensure that they have an email security solution in place and regularly train employees on phishing threats, as well as conduct simulated phishing tests.”