Investigating Ransomware with ProcDOT | TryHackMe Dunkle Materie

Introduction

In this walk-through, we covered investigating BlackMatter ransomware with ProcDOT. You can use ProcDOT to visualize processes and conduct malware investigation.

The firewall alerted the Security Operations Center that one of the machines at the Sales department, which stores all the customers’ data, contacted the malicious domains over the network. When the Security Analysts looked closely, the data sent to the domains contained suspicious base64-encoded strings. The Analysts involved the Incident Response team in pulling the Process Monitor and network traffic data to determine if the host is infected. But once they got on the machine, they knew it was a ransomware attack by looking at the wallpaper and reading the ransomware note.

Can you find more evidence of compromise on the host and what ransomware was involved in the attack?

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Getting Started with Procdot

First, I introduce you to procdot, a powerful visualization tool for malware analysis. It works by taking two main inputs: a process monitor dump (in CSV format) and a Wireshark network capture (a PCAP file). By combining these, procdot creates a visual representation of everything that happened on the system, making it much easier to spot malicious activity. I explain how to generate these files by running Wireshark to capture network traffic while letting the malware execute, and then dumping the process monitor data.

Diving into the Analysis

With the setup out of the way, I fire up procdot and load the process monitor log. The first thing I do is look for any suspicious processes. I quickly spot a couple of odd-looking explorer.exe processes. One has a typo in the name (“explorer.exe” with an extra ‘e’), and another is making unusual external calls. These are my first clues! I note their Process IDs (PIDs), which are 644 and 7128.

Visualizing the Attack

Next, I generate a visualization graph in procdot. This is where the magic happens! The graph shows me exactly what the ransomware did, including which files it encrypted, where it sent data, and the original file path of the ransomware itself. By following the connections in the graph, I discover that the ransomware first executed from C:\Users\Sales\AppData\Local\Temp\explorer.exe.

Uncovering the C2 Infrastructure

The visualization also reveals that the suspicious explorer.exe process was communicating with external IP addresses. To find the command and control (C2) domains, I switch over to Wireshark and filter for HTTP POST requests. This leads me to the first C2 domain: mojobiden.com. I then use VirusTotal to find a second domain, paymenthacks.com. The IP addresses associated with these domains are 206.111.88.197 and 146.112.61.108.

More Forensic Details

Digging deeper into the Wireshark capture, I examine the TCP stream of a POST request and find that the user agent used for data exfiltration was Firefox 89.0. I also discover that a cloud security service, Cisco Umbrella, blocked one of the malicious domains, which is why I see a “403 Forbidden” response.

Ransomware Artifacts

Back in the procdot visualization, I find a registry key related to the desktop wallpaper. This reveals the name of the bitmap file used for the ransom note wallpaper: ldykpi9r.bmap. I also identify the PID of the thread that tried to change the wallpaper as 4892. Furthermore, I find the registry key for a mounted drive, which is HKLM\SYSTEM\MountedDevices\DosDevices\Z:.

Identifying the Ransomware

Finally, using the IP addresses and file hashes I’ve collected, I turn to AlienVault OTX to identify the ransomware family. The evidence points to it being BlackMatter.

Technical Commands

Here are the technical commands I used during the investigation:

• In Wireshark, to filter for HTTP POST requests:http.request.method == "POST"
• In the terminal, to perform a DNS lookup:nslookup

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