Mac OSX_DOK Malware: New Attack Targets Swiss Bank Customers On MacOS

A strand of malware designed to hit machines running MacOS is being used in a scheme to target customers at Swiss banks in an attempt to gain access to their accounts.

The malware, discovered by security firm TrendMicro and dubbed OSX_DOK, is a variant of another form of malware used during an ongoing assault on patrons of Swiss banks, where a number of security vulnerabilities have been targeted by attackers.

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OSX_DOK arrives on a victim’s machine as part of a phishing scheme. It is delivered via email alongside a compromised .zip or .docx file that purports to be either a Mac app or a Microsoft Word document.

In both instances of the email attachments, the files are just means of getting the malicious software onto the victim’s device. If opened, the .zip file or .docx file will begin installing the malware onto the user’s machine.

Once it has executed, OSX_DOK displays a fake MacOS update screen that claims to address a security issue. If the user clicks the “Update All” button on the fake update request, they will be asked to enter the administrator password to carry out the installation. Doing so gives the malware the ability to gain high-level access to the machine.

In order to continue to establish its presence on a victim’s machine, OSX_DOK begins to download other utilities that are used to perform man-in-the-middle attacks, stealing information from the user as they browse the web and access their accounts.

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The malware, once fully engrained into a victim’s computer, takes a particular interest in internet traffic originating from Switzerland. Security researchers believe OSX_DOK is used to target patrons at Swiss banks in order to steal their credentials and gain access to their accounts.

To do this, the malware will intercept activity on a number of Swiss banking sites and redirect a victim to a site designed to look and act like the standard login page of their bank. Instead, the site steals the information the bank customer enters.

A previous attack on Swiss bank customers called Operation Emmental was able to bypass two-factor authentication by tricking victims into installing a fake app that would intercept authorization tokens. According to Trend Micro, OSX_DOK does not appear to use the same tactic but is technically capable of doing so.

Trend Micro theorized OSX_DOK is a Mac-targeted version of a known online banking malware called WERDLOD, which is used to target Windows machines. The attacks behave similarly and target similar victims, according to the researchers.

“Both WERDLOD and OSX_DOK targeted financial institutions, with a particular focus on banks in Switzerland,” the researchers said. “While it’s possible that this is a coincidence, the rest of the evidence makes it unlikely for these two malware to target the same organizations by chance.”

OSX_DOC is just the latest in a growing number of malicious attacks designed for MacOS. While Apple’s operating system still lags well behind Windows in total number of threats, Macs are increasingly becoming the target of malware campaigns. A recent report identified a 370 percent leap in threats targeting Macs in 2016.