A new phishing campaign known as CRON#TRAP is making waves in the cybersecurity landscape by targeting Windows systems through the stealthy installation of backdoored Linux virtual machines (VMs). Discovered by researchers at Securonix, this campaign employs phishing emails masquerading as invitations to a “OneAmerica survey.” The emails contain a sizable ZIP archive, which, when extracted, deploys a QEMU-managed TinyCore Linux VM named “PivotBox.” This innovative approach allows threat actors to breach corporate networks and gain persistent access without requiring manual intervention, a significant shift from traditional attack methods.
The ZIP archive includes a Windows shortcut disguised as “OneAmerica Survey.lnk” and a folder containing the QEMU application. When users click the shortcut, a PowerShell command is executed, extracting the contents to a specified user directory and launching a batch file that sets up the Linux VM. While the installation occurs, a decoy PNG image is displayed to mislead users into thinking the process is related to the survey. This tactic exploits user trust and enhances the likelihood of successful installation without raising alarms.
Once deployed, the “PivotBox” VM operates in the background, equipped with a backdoor called Chisel, which enables secure communication with a command-and-control (C2) server. Chisel facilitates the tunneling of data over HTTP and SSH, allowing attackers to maintain communication with compromised hosts even if firewalls are in place. Furthermore, the QEMU environment is configured for persistence, ensuring the backdoor remains active after system reboots. This method gives attackers the ability to execute commands, perform file management, and conduct data exfiltration activities seamlessly.
To mitigate the risks posed by the CRON#TRAP campaign, cybersecurity experts recommend implementing several defensive measures. Organizations should monitor for any instances of the QEMU process being executed from user-accessible folders and consider blacklisting QEMU and similar virtualization software on critical systems. Additionally, disabling virtualization features in BIOS settings can further protect against unauthorized installations of such VMs. By adopting these strategies, businesses can enhance their defenses against increasingly sophisticated phishing attacks and safeguard their networks from potential breaches.
Reference:
