Sarah Chen — Malware Reverse Engineer
Key Takeaways
- Initial access was gained via a phishing email with a malicious attachment.
- The ransomware employed sophisticated C2 communications through DNS tunneling.
- Lateral movement was facilitated by exploiting Windows administrative tools and weak credential policies.
Executive Summary
In our recent investigation of a ransomware incident affecting multiple organizations, we observed a well-coordinated attack chain leveraging various techniques to ensure persistence, lateral movement, and ultimately data exfiltration. The actor initiated the breach through a meticulously crafted phishing campaign, which exploited human vulnerabilities before deploying a highly evasive ransomware payload. Our analysis revealed multiple indicators of compromise (IOCs) that can aid the detection of similar threats in the future.
Initial Access
During the investigation, we dissected the initial attack vector which relied heavily on social engineering. The attacker sent phishing emails to employees within the targeted organizations, featuring an Excel file with macros enabled. Once the victim opened the attachment, the macro executed a PowerShell command that downloaded the malicious payload from a remote server. This phase of the attack exemplifies the use of T1566 – Phishing, showcasing how adversaries can deceive users into executing their malware.
Execution & Persistence
After the initial compromise, the sample we examined employed several techniques to execute and maintain persistence. The downloaded payload was a variant of a well-known ransomware, which upon execution, created a scheduled task at C:\Windows\System32\Tasks\RansomwareTask. This task was configured to run every 30 minutes, ensuring the implant was always active on the victim’s system. Furthermore, we observed that the ransomware modified registry keys at HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run, adding its executable to the startup process with the value
Source: Original Report