CISA warns of phishing attacks delivering KONNI RAT

Pierluigi Paganini August 17, 2020

The Cybersecurity and Infrastructure Security Agency (CISA) has issued an alert related to attacks delivering the KONNI remote access Trojan (RAT).

The Cybersecurity and Infrastructure Security Agency (CISA) has published an alert to provide technical details on a new wave of attacks delivering the KONNI remote access Trojan (RAT).

The KONNI RAT was first discovered in May 2017 by researchers from the Cisco Talos team after it was employed in attacks aimed at organizations linked to North Korea.

The malware has evolved over the years, it is able to log keystrokes, steal files, capture screenshots, collect information about the infected system, steal credentials from major browsers (i.e. Chrome, Firefox, and Opera), and remotely execute arbitrary code.

The malware has been active since at least 2014, it was undetected for more than 3 years and was used in highly targeted attacks.

The KONNI malware also employed in at least two campaigns in 2017. Threat actors used a decoy document titled “Pyongyang e-mail lists – April 2017” and it contained the email addresses and phone numbers of individuals working at organizations such as the United Nations, UNICEF and embassies linked to North Korea.

Hackers also used a second decoy document, titled “Inter Agency List and Phonebook – April 2017” contained names and contact information for members of agencies, embassies and other organizations linked to North Korea.

Experts at Cylance noticed that the decoy document titled “Pyongyang e-mail lists – April 2017, presents many similarities with a document used in a campaign that experts at Bitdefender linked to DarkHotel.

The first Darkhotel espionage campaign was spotted by experts at Kaspersky Lab in late 2014, according to the researchers the APT group has been around for nearly a decade while targeting selected corporate executives traveling abroad.

Now experts from CISA are warning of phishing messages delivering weaponized Microsoft Word documents that contain malicious Visual Basic Application (VBA) macro code. Upon enabling the macros, the code will fetch and install the KONNI malware.

Government experts warn that macro code could change the font color to trick the victim into enabling content and determine the system architecture.

“The Cybersecurity and Infrastructure Security Agency (CISA) has observed cyber actors using emails containing a Microsoft Word document with a malicious Visual Basic Application (VBA) macro code to deploy KONNI malware.” reads the CISA’s alert. “The malicious code can change the font color from light grey to black (to fool the user to enable content), check if the Windows operating system is a 32-bit or 64-bit version, and construct and execute the command line to download additional files (Command and Scripting Interpreter: Windows Command Shell [T1059.003]).”

The VBA macro uses the certificate database tool CertUtil for the download of remote files from a given Uniform Resource Locator.

The experts noticed that the tool incorporates a built-in function to decode base64-encoded files, which is used by the attackers. The Command Prompt copies certutil.exe into a temp directory and renames it to evade detection.

The attackers then download a text file containing a base64-encoded string that is decoded by CertUtil and saved as a batch (.BAT) file. As a last step of the attack, the cyber actor deletes the text file and executes the .BAT file.

CISA alert also includes a list of MITRE ATT&CK techniques associated with KONNI RAT and Snort signatures for use in detecting KONNI malware exploits.

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Pierluigi Paganini

(SecurityAffairs – hacking, KONNI RAT)

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