Fake Zoom Ends in BlackSuit Ransomware
Summary:
DFIR Report researchers shared details of an intrusion that occurred in May 2024, where actors leveraged a fake zoom installer to infect the targeted system with BlackSuit ransomware. The attack initiated when an unsuspecting victim visited a malicious site masquerading Zoom’s official download page (zoommanager[.]com). Clicking on the download button initiated the installation of a malicious program (d3f@ck loader) created with Inno Setup. A batch script was then executed to exclude the payload folder from Windows Defender, ensuring persistence. The malicious program subsequently reached out to a Steam Community page to obtain the next-stage IP address, followed by another script that downloaded and extracted two archive files. One of the archives ran the legitimate Zoom installer, masking the attack and reducing the likelihood of detection by IT or security teams. The second archive executed the IDAT loader, which decrypted and injected SectopRAT into the MSBuild.exe process, further establishing communication to a command and control server. After eight days, SectopRAT triggered the execution of Brute Ratel and Cobalt Strike, allowing the attacker to move laterally through the network. Using QDoor, a proxy tool, the attacker facilitated RDP access to multiple servers, exfiltrating data via Bublup and preparing to deploy BlackSuit ransomware. The ransomware was then spread across systems using PsExec, encrypting files and deleting shadow copies. In total, researchers note, the entire attack spanned 194 hours, culminating in the deployment of ransomware on both remote hosts and the domain controller.
Security Officer Comments:
The latest development highlights a trend in actors setting up fake download pages for legitimate software like Zoom, which is widely used by organizations. These fraudulent sites are often promoted through Google Ads, allowing attackers to purchase advertisements that place their malicious pages at the top of search engine results, thus increasing the likelihood of unsuspecting victims visiting them. In this particular intrusion, the actors went a step further by ensuring that the legitimate Zoom program was installed alongside the malware binaries, creating the illusion of a normal installation process and lowering the chances of the end user suspecting anything malicious. To further evade detection, the attackers maintained a low profile for eight days after initial communication with the command and control server, allowing them to blend into the victim's environment before executing further stages of the attack. Overall, this delay in activity highlights the actors’ patience and strategic approach to maintaining persistence within the compromised system.
Suggested Corrections:
Backup your data, system images, and configurations, regularly test them, and keep the backups offline: Ensure that backups are regularly tested and that they are not connected to the business network, as many ransomware variants try to find and encrypt or delete accessible backups. Maintaining current backups offline is critical because if your network data is encrypted with ransomware, your organization can restore systems.
Update and patch systems promptly: This includes maintaining the security of operating systems, applications, and firmware in a timely manner. Consider using a centralized patch management system; use a risk-based assessment strategy to drive your patch management program.
Test your incident response plan: There's nothing that shows the gaps in plans more than testing them. Run through some core questions and use those to build an incident response plan: Are you able to sustain business operations without access to certain systems? For how long? Would you turn off your manufacturing operations if business systems such as billing were offline?
Check your security team's work: Use a 3rd party pen tester to test the security of your systems and your ability to defend against a sophisticated attack. Many ransomware criminals are aggressive and sophisticated and will find the equivalent of unlocked doors.
Segment your networks: There's been a recent shift in ransomware attacks – from stealing data to disrupting operations. It's critically important that your corporate business functions and manufacturing/production operations are separated and that you carefully filter and limit internet access to operational networks, identify links between these networks, and develop workarounds or manual controls to ensure ICS networks can be isolated and continue operating if your corporate network is compromised. Regularly test contingency plans such as manual controls so that safety-critical functions can be maintained during a cyber incident.
Train employees: Email remains the most vulnerable attack vector for organizations. Users should be trained on how to avoid and spot phishing emails. Multi-factor authentication can help prevent malicious access to sensitive services.
Implement multi-factor authentication (MFA): External-facing assets that leverage single-factor authentication (SFA) are highly susceptible to brute-forcing attacks, password spraying, or unauthorized remote access using valid (stolen) credentials. Implementing MFA enhances security and adds an extra layer of protection.
Link(s):
https://thedfirreport.com/2025/03/31/fake-zoom-ends-in-blacksuit-ransomware/
DFIR Report researchers shared details of an intrusion that occurred in May 2024, where actors leveraged a fake zoom installer to infect the targeted system with BlackSuit ransomware. The attack initiated when an unsuspecting victim visited a malicious site masquerading Zoom’s official download page (zoommanager[.]com). Clicking on the download button initiated the installation of a malicious program (d3f@ck loader) created with Inno Setup. A batch script was then executed to exclude the payload folder from Windows Defender, ensuring persistence. The malicious program subsequently reached out to a Steam Community page to obtain the next-stage IP address, followed by another script that downloaded and extracted two archive files. One of the archives ran the legitimate Zoom installer, masking the attack and reducing the likelihood of detection by IT or security teams. The second archive executed the IDAT loader, which decrypted and injected SectopRAT into the MSBuild.exe process, further establishing communication to a command and control server. After eight days, SectopRAT triggered the execution of Brute Ratel and Cobalt Strike, allowing the attacker to move laterally through the network. Using QDoor, a proxy tool, the attacker facilitated RDP access to multiple servers, exfiltrating data via Bublup and preparing to deploy BlackSuit ransomware. The ransomware was then spread across systems using PsExec, encrypting files and deleting shadow copies. In total, researchers note, the entire attack spanned 194 hours, culminating in the deployment of ransomware on both remote hosts and the domain controller.
Security Officer Comments:
The latest development highlights a trend in actors setting up fake download pages for legitimate software like Zoom, which is widely used by organizations. These fraudulent sites are often promoted through Google Ads, allowing attackers to purchase advertisements that place their malicious pages at the top of search engine results, thus increasing the likelihood of unsuspecting victims visiting them. In this particular intrusion, the actors went a step further by ensuring that the legitimate Zoom program was installed alongside the malware binaries, creating the illusion of a normal installation process and lowering the chances of the end user suspecting anything malicious. To further evade detection, the attackers maintained a low profile for eight days after initial communication with the command and control server, allowing them to blend into the victim's environment before executing further stages of the attack. Overall, this delay in activity highlights the actors’ patience and strategic approach to maintaining persistence within the compromised system.
Suggested Corrections:
Backup your data, system images, and configurations, regularly test them, and keep the backups offline: Ensure that backups are regularly tested and that they are not connected to the business network, as many ransomware variants try to find and encrypt or delete accessible backups. Maintaining current backups offline is critical because if your network data is encrypted with ransomware, your organization can restore systems.
Update and patch systems promptly: This includes maintaining the security of operating systems, applications, and firmware in a timely manner. Consider using a centralized patch management system; use a risk-based assessment strategy to drive your patch management program.
Test your incident response plan: There's nothing that shows the gaps in plans more than testing them. Run through some core questions and use those to build an incident response plan: Are you able to sustain business operations without access to certain systems? For how long? Would you turn off your manufacturing operations if business systems such as billing were offline?
Check your security team's work: Use a 3rd party pen tester to test the security of your systems and your ability to defend against a sophisticated attack. Many ransomware criminals are aggressive and sophisticated and will find the equivalent of unlocked doors.
Segment your networks: There's been a recent shift in ransomware attacks – from stealing data to disrupting operations. It's critically important that your corporate business functions and manufacturing/production operations are separated and that you carefully filter and limit internet access to operational networks, identify links between these networks, and develop workarounds or manual controls to ensure ICS networks can be isolated and continue operating if your corporate network is compromised. Regularly test contingency plans such as manual controls so that safety-critical functions can be maintained during a cyber incident.
Train employees: Email remains the most vulnerable attack vector for organizations. Users should be trained on how to avoid and spot phishing emails. Multi-factor authentication can help prevent malicious access to sensitive services.
Implement multi-factor authentication (MFA): External-facing assets that leverage single-factor authentication (SFA) are highly susceptible to brute-forcing attacks, password spraying, or unauthorized remote access using valid (stolen) credentials. Implementing MFA enhances security and adds an extra layer of protection.
Link(s):
https://thedfirreport.com/2025/03/31/fake-zoom-ends-in-blacksuit-ransomware/