Malware Analysis – AppleJeus: Dorusio

This Malware Analysis Report (MAR) is the result of analytic efforts among the Federal Bureau of Investigation (FBI), the Cybersecurity and Infrastructure Security Agency (CISA), and the Department of Treasury (Treasury) to highlight the cyber threat to cryptocurrency posed by North Korea, formally known as the Democratic People’s Republic of Korea (DPRK), and provide mitigation recommendations. Working with U.S. government partners, FBI, CISA, and Treasury assess that Lazarus Group—which these agencies attribute to North Korean state-sponsored advanced persistent threat (APT) actors—is targeting individuals and companies, including cryptocurrency exchanges and financial service companies, through the dissemination of cryptocurrency trading applications that have been modified to include malware that facilitates theft of cryptocurrency.

This MAR highlights this cyber threat posed by North Korea and provides detailed indicators of compromise (IOCs) used by the North Korean government. The U.S. Government refers to malicious cyber activity by the North Korean government as HIDDEN COBRA. For more information on other versions of AppleJeus and recommended steps to mitigate this threat, see Joint Cybersecurity Advisory AA21-048A: AppleJeus: Analysis of North Korea’s Cryptocurrency Malware at https://www.us-cert.cisa.gov/ncas/alerts/AA21-048A.

There have been multiple versions of AppleJeus malware discovered since its initial discovery in August 2018. In most versions, the malware appears to be from a legitimate-looking cryptocurrency trading company and website, whereby an unsuspecting individual downloads a third-party application from a website that appears legitimate.

The U.S. Government has identified AppleJeus malware version—Dorusio—and associated IOCs used by the North Korean government in AppleJeus operations. Some information has been redacted from this report to preserve victim anonymity.

Dorusio, discovered in March 2020, is a legitimate-looking cryptocurrency trading software that is marketed and distributed by a company and website— Dorusio Wallet and dorusio[.]com, respectively—that appear legitimate. There are Windows and OSX versions of Dorusio Wallet. As of at least early 2020, the actual download links result in 404 errors. The download page has release notes with version revisions claiming to start with Version 1.0.0, which was released on April 15, 2019.

For a downloadable copy of IOCs, see: MAR-10322463-6.v1.stix.

Submitted Files (6)

[Redacted] (dorusio_osx_v2.1.0.dmg)

21afaceee5fab15948a5a724222c948ad17cad181bf514a680267abcce186831 (DorusioUpgrade.exe)

[Redacted] (dorusio_win_v2.1.0.msi)

78b56a1385f2a92f3c9404f71731088646aac6c2c84cc19a449976272dab418f (Dorusio.exe)

a0c461c94ba9f1573c7253666d218b3343d24bfa5d8ef270ee9bc74b7856e492 (Dorusio)

dcb232409c799f6ddfe4bc0566161c2d0b372db6095a0018e6059e34c2b79c61 (dorusio_upgrade)

Domains (1)

dorusio.com

[Redacted]

Tags

droppertrojan

Details

Antivirus

No matches found.

YARA Rules

No matches found.

ssdeep Matches

No matches found.

Relationships

Description

This Windows program from the Dorusio Wallet site is a Windows MSI Installer. This installer appears to be legitimate and will install “Dorusio.exe” (78b56a1385f2a92f3c9404f71731088646aac6c2c84cc19a449976272dab418f) in the “C:\Program Files (x86)\Dorusio” folder. It will also install “DorusioUpgrade.exe” (21afaceee5fab15948a5a724222c948ad17cad181bf514a680267abcce186831) in the “C:\Users\<username>\AppData\Roaming\DorusioSupport” folder. Immediately after installation, the installer launches “DorusioUpgrade.exe.” During installation, a Dorusio folder containing the “Dorusio.exe” application is added to the start menu.

Screenshots

dorusio.com

Tags

command-and-control

URLs

• dorusio.com/dorusio_update.php

Whois

Whois for dorusio.com had the following information:
Registrar: NAMECHEAP INC
Creation Date: 2020-03-30
Registrar Registration Expiration Date: 2021-03-30

Relationships

Description

The domain “dorusio.com” had a legitimately signed Sectigo SSL certificate, which was “Domain Control Validated” similar to the domain certificates for previous AppleJeus domain certificates. Investigation revealed the point of contact listed for verification was support[@]dorusio.com. No other contact information was available as the administrative or technical contact for the domain.

The domain is registered with NameCheap at the IP address 198.54.115.51 with ASN 22612. This IP is on the same ASN as the AppleJeus version 5 “CoinGoTrade” IP address.

Screenshots

78b56a1385f2a92f3c9404f71731088646aac6c2c84cc19a449976272dab418f

Tags

trojan

Details

Antivirus

No matches found.

YARA Rules

No matches found.

ssdeep Matches

PE Metadata

PE Sections

Packers/Compilers/Cryptors

Relationships

Description

This file is a 64-bit Windows executable contained within the Windows MSI Installer “dorusio_win_v2.1.0.msi.” When executed, “Dorusio.exe” loads a legitimate looking cryptocurrency wallet application with no signs of malicious activity. Aside from the “Dorusio” logo and two new services, the wallet appears to be the same as the AppleJeus version 4 “Kupay wallet.”

This application appears to be a modification of the opensource cryptocurrency wallet Copay, which is distributed by Atlanta based company BitPay. According to the website “bitpay.com,” “BitPay builds powerful, enterprise-grade tools for crypto acceptance and spending”.

In addition to application appearance being similar, a DNS request for “bitpay.com” is always sent out immediately after a DNS request for “dorusio.com” and the company listed for “Dorusio” is Bitpay.

In addition, the GitHub “Commit Hash” listed in the “Dorusio” application “638b2b1” is to a branch of Copay found at hxxps[:]//github.com/flean/copay-1.

Screenshots

21afaceee5fab15948a5a724222c948ad17cad181bf514a680267abcce186831

Tags

trojan

Details

Antivirus

YARA Rules

No matches found.

ssdeep Matches

No matches found.

PE Metadata

PE Sections

Packers/Compilers/Cryptors

Relationships

Description

This file is a 64-bit Windows executable contained within the Windows MSI Installer “dorusio_win_v2.1.0.msi.” When executed, “DorusioUpgrade.exe” first installs itself as a service, which will automatically start when any user logs on. The service is installed with a description of “Automatic Dorusio Upgrade.”

After installing the service, “DorusioUpgrade.exe” has similar behavior to the upgrade components of Kupay Wallet (AppleJeus variant 4) and CoinGoTrade (AppleJeus variant 5). On startup, “DorusioUpgrade.exe” allocates memory in order to later write a file. After allocating the memory and storing the hardcoded string “Latest” in a variable, the program attempts to open a network connection. The connection is named “Dorusio Wallet 2.1.0 (Check Update Windows)”, likely to avoid suspicion from a user.

Similar to previous AppleJeus variants, “DorusioUpgrade.exe” collects some basic information from the system as well as a timestamp and places them in hard-coded format strings. Specifically, the timestamp is placed into a format string “ver=%d&timestamp=%lu” where ver is set as the 201000, possibly referring to the Dorusio Wallet version previously mentioned (Figure 5).

This basic information and hard-coded strings are sent via a POST to the command and control (C2) “dorusio.com/dorusio_update.php.” If the POST is successful (i.e. returns an HTTP response status code of 200) but fails any of multiple different checks, “DorusioUpgrade.exe” will sleep for two minutes and then regenerate the timestamp and contact the C2 again.

After receiving the payload from the C2, the program writes the payload to memory and executes the payload.

The payload could not be downloaded as the C2 server dorusio.com/dorusio_update.php is no longer accessible. In addition, the sample was not identified in open source reporting for this sample.

Screenshots

[Redacted]

Tags

droppertrojan

Details

Antivirus

No matches found.

YARA Rules

No matches found.

ssdeep Matches

No matches found.

Relationships

Description

This OSX program from the Dorusio Wallet site is an Apple DMG installer. The OSX program does not has a digital signature and will warn the user of that before installation. As all previous versions of AppleJeus, the Dorusio Wallet installer appears to be legitimate, and installs both “Dorusio” (a0c461c94ba9f1573c7253666d218b3343d24bfa5d8ef270ee9bc74b7856e492) in the “/Applications/Dorusio.app/Contents/MacOS/” folder and a program named “dorusio_upgrade” (dcb232409c799f6ddfe4bc0566161c2d0b372db6095a0018e6059e34c2b79c61) also in the “/Applications/Dorusio.app/Contents/MacOS/” folder. The installer contains a postinstall script (Figure 7).

The postinstall script is identical in functionality to the postinstall scripts from previous AppleJeus variants and is identical to the CoinGoTrade (version 5) postinstall script. The postinstall script creates a “DorusioDaemon” folder in the OSX “/Library/Application Support” folder and moves “dorusio_upgrade” to it. The “Application Support” folder contains both system and third-party support files which are necessary for program operation. Typically, the subfolders have names matching those of the actual applications. At installation, Dorusio placed the plist file (com.dorusio.pkg.wallet.plist) in “/Library/LaunchDaemons/.”

As the LaunchDaemon will not be run immediately after the plist file is moved, the postinstall script then launches the dorusio_upgrade program in the background.

Screenshots

a0c461c94ba9f1573c7253666d218b3343d24bfa5d8ef270ee9bc74b7856e492

Tags

trojan

Details

Antivirus

No matches found.

YARA Rules

No matches found.

ssdeep Matches

No matches found.

Description

This OSX sample was contained within Apple DMG installer “dorusio_osx_v2.1.0.dmg.” Similar to the Windows version, “Dorusio” is likely a copy of Copay from BitPay and is almost identical to the AppleJeus variant 4 OSX “Kupay” program.

dcb232409c799f6ddfe4bc0566161c2d0b372db6095a0018e6059e34c2b79c61

Tags

trojan

Details

Antivirus

YARA Rules

No matches found.

ssdeep Matches

No matches found.

Relationships

Description

This OSX sample was contained within Apple DMG installer “dorusio_osx_v2.1.0.dmg.” The program “dorusio_upgrade” is similar to AppleJeus variant 4 OSX sample “kupay_upgrade” and AppleJeus variant 5 OSX sample “CoinGoTradeUpgradeDaemon.”When executed, “dorusio_upgrade” immediately sleeps for five seconds then tests to see if the hard-coded value stored in “isReady” is a 0 or a 1. If it is a 0, the program sleeps again, and if it is a 1, the function “CheckUpdate” is called. This function contains most of the logic functionality of the malware. “CheckUpdate” sends a POST to the C2 hxxps[:]//dorusio.com/dorusio_update.php with a connection named “Dorusio Wallet 2.1.0 (Check Update Osx).

Just as the Kupay and CoinGoTrade malware, the timestamp is placed into a format string “ver=%d&timestamp=%ld” where ver is set as the 20100, possibly referring to the Dorusio Wallet version previously mentioned.

If the C2 server returns a file, it is decoded and written to /private/tmp/dorusio_update,” with permissions by the command “chmod 700” (only the user can read, write, and execute). The stage2 (/private/tmp/dorusio_update) is then launched and the malware dorusio_upgrade returns to sleeping and checking in with the C2.

The payload could not be downloaded as the C2 server dorusio.com/dorusio_update.php is no longer accessible. In addition, the sample was not identified in open source reporting for this sample.

Screenshots

CISA recommends that users and administrators consider using the following best practices to strengthen the security posture of their organization’s systems. Any configuration changes should be reviewed by system owners and administrators prior to implementation to avoid unwanted impacts.

• Maintain up-to-date antivirus signatures and engines.
• Keep operating system patches up-to-date.
• Disable File and Printer sharing services. If these services are required, use strong passwords or Active Directory authentication.
• Restrict users’ ability (permissions) to install and run unwanted software applications. Do not add users to the local administrators group unless required.
• Enforce a strong password policy and implement regular password changes.
• Exercise caution when opening e-mail attachments even if the attachment is expected and the sender appears to be known.
• Enable a personal firewall on agency workstations, configured to deny unsolicited connection requests.
• Disable unnecessary services on agency workstations and servers.
• Scan for and remove suspicious e-mail attachments; ensure the scanned attachment is its “true file type” (i.e., the extension matches the file header).
• Monitor users’ web browsing habits; restrict access to sites with unfavorable content.
• Exercise caution when using removable media (e.g., USB thumb drives, external drives, CDs, etc.).
• Scan all software downloaded from the Internet prior to executing.
• Maintain situational awareness of the latest threats and implement appropriate Access Control Lists (ACLs).

Additional information on malware incident prevention and handling can be found in National Institute of Standards and Technology (NIST) Special Publication 800-83, “Guide to Malware Incident Prevention & Handling for Desktops and Laptops”.