Kimsuky Hackers Spotted Using 3 New Android Malware to Target South Koreans

The North Korean espionage-focused actor known as Kimsuky has been observed using three different Android malware strains to target users located in its southern counterpart.

That's according to findings from South Korean cybersecurity company S2W, which named the malware families FastFire, FastViewer, and FastSpy.

"The FastFire malware is disguised as a Google security plugin, and the FastViewer malware disguises itself as 'Hancom Office Viewer,' [while] FastSpy is a remote access tool based on AndroSpy," researchers Lee Sebin and Shin Yeongjae said.

Kimsuky, also known by the names Black Banshee, Thallium, and Velvet Chollima, is believed to be tasked by the North Korean regime with a global intelligence-gathering mission, disproportionately targeting individuals and organizations in South Korea, Japan, and the U.S.

This past August, Kaspersky unearthed a previously undocumented infection chain dubbed GoldDragon to deploy a Windows backdoor capable of stealing information from the victim such as file lists, user keystrokes, and stored web browser login credentials.

The advanced persistent threat is also known to an Android version of AppleSeed implant to execute arbitrary actions and exfiltrate information from the infected devices.

FastFire, FastViewer, and FastSpy are the latest additions to its evolving Android malware arsenal, which are designed to receive commands from Firebase and download additional payloads.

"FastViewer is a repackaged APK by adding arbitrary malicious code inserted by an attacker to the normal Hancom Office Viewer app," the researchers said, adding the malware also downloads FastSpy as a next-stage.

The rogue apps in question are below -

• com.viewer.fastsecure (Google 보안 Plugin)
• com.tf.thinkdroid.secviewer (FastViewer)

Both FastViewer and FastSpy abuse Android's accessibility API permissions to fulfill its spying behaviors, with the latter automating user clicks to grant itself extensive permissions in a manner analogous to MaliBot.

FastSpy, once launched, enables the adversary to seize control of the targeted devices, intercept phone calls and SMSes, track users' locations, harvest documents, capture keystrokes, and record information from the phone's camera, microphone, and speaker.

S2W's attribution of the malware to Kimsuky is based on overlaps with a server domain named "mc.pzs[.]kr," which was previously employed in a May 2022 campaign identified as orchestrated by the group to distribute malware disguised as North Korea related press releases.

"Kimsuky group has continuously performed attacks to steal the target's information targeting mobile devices," the researchers said. "In addition, various attempts are being made to bypass detection by customizing Androspy, an open source RAT."

"Since Kimsuky group's mobile targeting strategy is getting more advanced, it is necessary to be careful about sophisticated attacks targeting Android devices."