Hackers are using a fake PDF viewer to infect Macs with malware — how to stay safe

MacBook Pro 16-inch 2021 sitting on a patio table
(Image credit: Tom's Guide)

Hackers continue to set their sights on Macs and this time around, they’re using a new macOS malware to infect unsuspecting users.

As reported by The Hacker News, the North Korea-based BlueNoroff (a subgroup of the infamous Lazarus hacking group) is targeting Mac users with a new malware strain dubbed RustBucket.

First discovered by security researchers at the cybersecurity firm Jamf, RustBucket is a stage-one malware that is able to download additional payloads from a command and control (C&C) server controlled by the hackers behind this campaign.

If you use one of the best MacBooks or even a Mac Mini, you’re going to want to be careful when checking your email as the RustBucket malware is delivered via a fake PDF viewer application.

Disguised as an Internal PDF Viewer

The BlueNoroff hackers are using an unsigned application called “Internal PDF Viewer.app” to infect vulnerable Macs with the RustBucket malware. However, this internal PDF viewer app is just the first stage of the infection.

Once downloaded onto a Mac, RustBucket then retrieves the second-stage payload which is a signed application posing as a legitimate Apple bundle identifier from the hacker-controlled C&C server. To throw off potential victims, it also displays a decoy PDF with information from a legitimate venture capital firm.

From here, the malware then receives the stage-three payload which is a signed trojan that can run on both ARM and X86 systems since it’s written in the Rust programming language.

The RustBucket malware is capable of gathering system information from an infected Mac including a list of running processes, the current time and whether it’s running in a virtual machine.

In its report, Jamf provided further insight on the state of Mac malware, saying: “The malware used here shows that as macOS grows in market share, attackers realize that a number of victims will be immune if their tooling is not updated to include the Apple ecosystem. Lazarus group, which has strong ties to BlueNoroff, has a long history of attacking macOS and it’s likely we’ll see more APT groups start doing the same.”

How to keep your Mac safe from malware

A padlock resting next to the Apple logo on the lid of a gold-colored Apple laptop.

(Image credit: robert coolen/Shutterstock)

Just like on one of the best Windows laptops, when it comes to keeping your Mac safe from malware, you want to be extremely careful when checking your inbox. PDFs and other attachments are often used by hackers to spread malware which is why you should avoid opening any files in emails sent from an unknown sender. Likewise, you shouldn’t click on any links these emails contain either.

Although MacOS comes with XProtect to detect and block malware from running on your Apple computer and Gatekeeper to ensure that all software is signed by a developer registered with Apple, Mac malware does slip through the cracks from time to time. This is why you should also consider using one of the best Mac antivirus software solutions on your Apple computers.

As Jamf pointed out in its report, we’ll likely see more state-sponsored hackers targeting Macs now that Apple’s computers have become increasingly popular. For this reason, Mac users now need to be just as careful as Windows users to avoid having their systems infected with malware and their personal and financial information stolen by hackers.

More from Tom's Guide

TOPICS
Anthony Spadafora
Managing Editor Security and Home Office

Anthony Spadafora is the managing editor for security and home office furniture at Tom’s Guide where he covers everything from data breaches to password managers and the best way to cover your whole home or business with Wi-Fi. He also reviews standing desks, office chairs and other home office accessories with a penchant for building desk setups. Before joining the team, Anthony wrote for ITProPortal while living in Korea and later for TechRadar Pro after moving back to the US. Based in Houston, Texas, when he’s not writing Anthony can be found tinkering with PCs and game consoles, managing cables and upgrading his smart home. 

Read more
Malware
New macOS malware uses Apple's own code to quietly steal credentials and personal data — how to stay safe
MacBook Pro 2021 (16-inch) on a patio table
Macs under attack from dangerous malware targeting digital wallets and Apple’s Notes app — how to stay safe
MacBook Pro 2021 (16-inch) on a patio table
Millions of Mac owners urged to be on alert for info-stealing malware
MacBook Pro 2023
Macs under attack from North Korean malware stealing passwords and more — how to stay safe
A hacker typing quickly on a keyboard
Hackers are posing as Apple and Google to infect Macs with malware — don’t fall for these fake browser updates
MacBook Pro 2023
New Mac attack is tricking users into thinking their computer is locked — how to stay safe
Latest in Malware & Adware
Green skull on smartphone screen.
Malicious Android apps with 60 million installs bombarding phones with ads and phishing attacks — how to stay safe
Malware
Dangerous new password-stealing trojan automatically reinstalls itself on infected PCs
An FBI agent typing on a computer
FBI issues warning to millions of Americans to avoid these websites that can steal your passwords and banking info
A hacker typing quickly on a keyboard
New MassJacker malware is hijacking digital wallets to steal large sums from users
A person trying to set up a new Wi-Fi router
Thousands of TP-Link routers have been infected by a botnet to spread malware
A smartphone screen displaying the Android name and logo next to a sign reading 'MALWARE'.
Fake Google Play Store pages are spreading Trojan malware that can steal your financial data
Latest in News
Tom Hiddleston as Robert Laing in "High Rise" now streaming on Netflix
5 best Netflix movies in March you haven't watched yet
iPhone 16 with Apple Intelligence logo for iOS 18.1
iOS 18.4: All the newest Apple Intelligence features coming to your iPhone
Maria Debska in "Just One Look" now streaming on Netflix
3 best Netflix shows in March you haven't watched yet
Split image featuring the Galaxy S25 Edge (left) and Galaxy S25 Ultra (right)
Samsung Galaxy S25 Edge just tipped for two Galaxy S25 Ultra-level features
Wolfenstein: The Old Blood
Amazon is giving away a ton of free games for its Big Spring Sale — here’s how to claim yours
A TV with the Netflix logo sits behind a hand holding a remote
Netflix is rolling out a big video quality upgrade — what you need to know