CVE-2024-3400: PAN-OS Command Injection Vulnerability in GlobalProtect Gateway. Learn More

CVE-2024-3400: PAN-OS Command Injection Vulnerability in GlobalProtect Gateway. Learn More

Managed Detection & Response

Eliminate active threats with 24/7 threat detection, investigation, and response.

Co-Managed SOC (SIEM)

Maximize your SIEM investment, stop alert fatigue, and enhance your team with hybrid security operations support.

Advisory & Diagnostics

Advance your cybersecurity program and get expert guidance where you need it most.

Penetration Testing

Test your physical locations and IT infrastructure to shore up weaknesses before exploitation.

Database Security

Prevent unauthorized access and exceed compliance requirements.

Email Security

Stop email threats others miss and secure your organization against the #1 ransomware attack vector.

Digital Forensics & Incident Response

Prepare for the inevitable with 24/7 global breach response in-region and available on-site.

Firewall & Technology Management

Mitigate risk of a cyberattack with 24/7 incident and health monitoring and the latest threat intelligence.

Offensive Security
Solutions to maximize your security ROI
Microsoft Exchange Server Attacks
Stay protected against emerging threats
Rapidly Secure New Environments
Security for rapid response situations
Securing the Cloud
Safely navigate and stay protected
Securing the IoT Landscape
Test, monitor and secure network objects
Why Trustwave
About Us
Awards and Accolades
Trustwave SpiderLabs Team
Trustwave Fusion Security Operations Platform
Trustwave Security Colony
Technology Alliance Partners
Key alliances who align and support our ecosystem of security offerings
Trustwave PartnerOne Program
Join forces with Trustwave to protect against the most advance cybersecurity threats
SpiderLabs Blog

Good things happen when Forensics and Malware Analysis work together.

The SpiderLabs Incident Response team worked a case earlier this year where previously unseen malware was discovered. This isn't all that unusual, but this case really showcased the cooperative talents inside of SpiderLabs.

The malware, named "mssvc.exe", was discovered onsite during memory analysis of a Windows 2003 Server. Nothing special here, the key to recognizing it as "suspicious" was that it had a valid "looking" process name but when you look a little bit closer, there are no valid Windows OS files named "mssvc.exe".

A quick look at the executable with "strings" turned up a few things that threw the red flag:


First: If the service description is "Windows RPC Assistant"(which I've never heard of) Why is the executable named "mssvc.exe"and why is the service named "rcpassist" ?

Second: Is that a regex embedded in the executable? (\d{15,19}=\d{13,})

And third: What is t5701.dat?

I couldn't answer all of these questions myself so I recovered all of the files necessary for analysis and turned them over to our reverse engineering team.

Within a couple of hours (because John, Josh and Ryan are that good) I had a handful of answers and, more importantly, a couple more important questions.

The big answers were:

"Yes, this is definitely a memory scraping malware that is looking for and aggregating credit card track data."

"Yes, that is a regex for credit card data." (we now call it "baby's first regex" because of its simplicity)

"t5701.dat is a trojan backdoor that provides command line access."

The big question posed was:

"Can you recover the \\HKEY_USER\.Default\CurrentUser registry key so that we can look at the configuration variables for the malware?"

I immediately answered with a "sure".

I already knew where to find that key.

It's the ntuser.dat file located in the "Default User" profile, right?


I extracted it, I opened it with Registry Viewer, I parsed it with regripper.


The keys that malware analysis wanted just didn't exist.

<Insert 2 hours of research here>

Very little is written about this registry hive. Once I finally figured out the right way to word my search, I found this post.

In short, the .Default user is not the same as the Default User. In fact, this is the "default" hive that is located with the rest of the Operating hives (SAM, System, Security and Software) in C:\Window\System32\config.

Once I opened it with Registry Viewer I immediately recognized some of the key names and the structure from ntuser.dat files that I have worked with in the past.

It looked so familiar that I decided to try to parse it with regripper and the defaults for the "nt user" hive.

It worked....perfectly.

C:\Windows\system32\config\default is not "like" an ntuser.datfile. It "is" the ntuser.dat file for the "System" user.

If I continue to see this malware I am planning to write a regripper plug into retrieve the information I need. For this one case I got everything we needed from the viewer.


Those encoded values translated to the processes being watched, the exfiltration timer, exfiltration server, dump file size, etc.

Law Enforcement was already involved and the investigation data was turned over to them at the customers request.

Score 1 for the good guys!

Latest SpiderLabs Blogs

EDR – The Multi-Tool of Security Defenses

This is Part 8 in my ongoing project to cover 30 cybersecurity topics in 30 weekly blog posts. The full series can be found here.

Read More

The Invisible Battleground: Essentials of EASM

Know your enemy – inside and out. External Attack Surface Management tools are an effective way to understand externally facing threats and help plan cyber defenses accordingly. Let’s discuss what...

Read More

Fake Dialog Boxes to Make Malware More Convincing

Let’s explore how SpiderLabs created and incorporated user prompts, specifically Windows dialog boxes into its malware loader to make it more convincing to phishing targets during a Red Team...

Read More