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PrivateLoader: Analyzing the Encryption and Decryption of a Modern Loader 
HomeMalware Analysis
PrivateLoader: Analyzing the Encryption and Decryption of a Modern Loader 

In this article, we delve into the inner workings of PrivateLoader, a notorious malicious loader family. We will explore the encryption and decryption processes utilized by this malware, particularly focusing on its ability to protect itself using VMProtect, as well as its decryption of loaded libraries. Let’s dive in! 


PrivateLoader analysis introduction 

PrivateLoader is a malicious loader family, written in C++ and first discovered in early 2021. 

It is known for distributing a wide range of malware, from simple information stealers to complex rootkits and spyware, utilizing payloads. 

The distribution of this type of malware is managed by the Pay-Per-Install (PPI) service, a popular tool within the cybercriminal ecosystem that generates revenue by adding payloads to malware. 

  • The code itself involves the decryption of loaded libraries. 
  • At present, there are two versions of PrivateLoader available: one protected by VMProtect, and a regular version. 
  • Every day, between 2 and 4 samples of this malware are uploaded. 

Static Analysis of the Source File 

SHA256: 27c1ed01c767f504642801a7e7a7de8d87dbc87dee88fbc5f6adb99f069afde4 

Using the Detect It Easy utility, we can see that the analyzed executable file is compiled in C++. There is no information about the packer, which could mean it was not possible to identify it. 

PrivateLoader's sample data
Fig. 1 – PrivateLoader’s sample data 

The next step is to search for unencrypted strings using the strings command: 

strings --encoding=l loader.exe 

Interesting strings detected in the executable file 
Fig. 2 – Interesting strings detected in the executable file 

Analyzing the discovered strings allows us to identify several interesting elements: 

  • A user-agent, which is likely used to masquerade as a legitimate browser application 
  • URL addresses for determining the current IP and geolocation 

PrivateLoader dynamic analysis with ANY.RUN 

We analyzed the sample in ANY.RUN interactive malware sandbox.  

Here’s a link to the task:

The process tree generated by the executable file appears as follows: 

PrivateLoader's process tree 
Fig 3. – PrivateLoader’s process tree 

Analyzing the process tree leads to the following conclusions: 

1. The main PrivateLoader process creates a child process named “FhuC750omh76YtB1xgR7diEy.exe”, whose executable file is located in the user’s “Pictures” directory (T1564 – Hide Artifacts): 

C:\Users\admin\Pictures\Minor Policy 

2. The created child process is added to the startup using Task Scheduler (T1053.005 – Scheduled Task/Job: Scheduled Task): 

schtasks /create /f /RU “admin” /tr “”C:\Program Files (x86)\ClipManagerP0\ClipManager_Svc.exe”” /tn “LOLPA4DESK HR” /sc HOURLY /rl HIGHEST 

The executable file of the child process was downloaded from the Internet (T1105 – Ingress Tool Transfer). We will not go into the detailed analysis of it. 

PrivateLoader downloaded payload 
Fig 4. – PrivateLoader downloaded payload 

Analyzing the HTTP requests, we can observe connections and data exchanges with the C2 server (T1071.001 – Application Layer Protocol): 

PrivateLoader  С2 addresses 
Fig. 5 – С2 addresses 

The content sent (as well as received) in POST requests consists of BASE64-encoded strings (T1132.001 – Data Encoding: Standard Encoding). Decoding these strings does not yield any readable results: 


Moving forward to the indicators, we can see that the malware steals user credentials from browsers (T1552.001 Credentials In Files): 

PrivateLoader Stealing data 
Fig. 6 – Stealing data 

Technical Analysis of PrivateLoader  

For the technical analysis, the following tasks were set: 

  1. Locate the C2 server within the code 
  1. Identify the encryption algorithms for the C2 server and, if possible, for strings as well. 
  1. Automate the decryption of the C2 server and strings 

The analysis of the executable file revealed that string encryption is done using the XOR algorithm (T1027 – Obfuscated Files or Information). Initially, the data and key are loaded into the stack, and then decrypted using the SIMD instruction “PXOR” and the “XMM” register. The result of the XOR operation is also stored in the stack. 

The three stages of C2 server decryption are shown below. 

  1. Loading encrypted data into the stack: 

PrivateLoader data
Fig. 7 – Data 

  1. Loading the encryption key into the stack: 

Key PrivateLoader
Fig. 8 – Key 

  1. Decrypting the C2 server using the “PXOR” instruction and saving the results in the stack: 

Decrypting PrivateLoader
Fig. 9 – Decrypting 

During the analysis process, it was also found that the method similar to C2 decryption is used to decrypt the following: 

  • Used API functions (T1027.007 – Obfuscated Files or Information: Dynamic API Resolution) 
  • Payloads 
  • URLs and more

Some of the analyzed samples are protected by VMProtect. The search for string decryption is complicated by the fact that the decryption data is located in one function, while the XOR and key are in another. Moreover, the key is always the same. 

Fig 10. – Decript VMprotect sample

Example of automating C2 server decryption of PrivateLoader 

To automate the extraction of data and configuration, we can use the Triton framework. It will emulate code blocks that contain all the necessary encrypted information.

You can find an example of a script for emulating a specific block in our GitHub repository. The output of the script will be the decrypted C2 server. 

PrivateLoader Script output
Fig 11. – Script output 

Therefore, by emulating all the code blocks that contain encrypted data, we can obtain a set of strings with the necessary information, including the C2 server. 

Extracting the PrivateLoader configuration 

In our service, you can view the configuration, which is extracted automatically: 

PrivateLoader configution and strings
 Fig. 12 – PrivateLoader configution and strings

The decrypted data includes C2 addresses and strings. The strings contain information such as: used libraries and their functions, registry keys, paths to crypto wallets and browsers, etc. 


In this article, we discussed encryption in PrivateLoader. 

Its main feature is the XOR of all strings it interacts with (C2, URLs, DLLs). Also, some samples are protected by VMprotect, which makes the code a bit more complex due to the use of many functions. 

If you’d like to read more content like this, read our LimeRAT Malware Analysis. Or check out our deep dive into the encryption and decryption process of XLoader/FormBook


Tactics Techniques Description 
Software discovery 
Software Discovery 
Searches for installed software 
in the system  
in the “Uninstall” key 
System Information 
Collects system data 
Command and Control 
Application Layer  
Sending collected data  
to the control server 
 T1105 Ingress Tool Transfer requests binary from the Internet 
 T1132.001 – Data Encoding:
Standard Encoding 
encode data with BASE64 
TA0006: Credential Access T1552.001: Credentials In Files Stealing of personal data – login data 
TA0005: Defense Evasion T1564  Hide Artifacts attempt to hide artifacts in user folder 
 T1027.007 – Obfuscated Files or
Information: Dynamic
API Resolution  
obfuscate then dynamically resolve API
functions called by their malware 
 T1027 – Obfuscated Files or Information attempt to make an executable or
file difficult to discover or
analyze by encrypting XOR 
TA0002: Execution T1053.005 – Scheduled
Task/Job: Scheduled Task 
abuse the Windows Task
Scheduler to create file in statup 


Title Description 
Name 27c1ed01c767f504642801a7e7a7de8d87dbc87dee88fbc5f6adb99f069afde4 exe 
MD5 6cc7d9664c1a89c58549e57b5959bb38 
SHA1 85b665c501b9ab38710050e9a5c1b6d2e96acccc 
SHA256 27c1ed01c767f504642801a7e7a7de8d87dbc87dee88fbc5f6adb99f069afde4 

Extracted URLs 

  • http://23[.]254[.]227[.]214/api/tracemap[.]php  
  • http://23[.]254[.]227[.]205/api/tracemap[.]php  
  • http://23[.]254[.]227[.]202/api/tracemap[.]php  
  • http://208[.]67[.]104[.]60/api/tracemap[.]php  
  • http://208[.]67[.]104[.]60/api/firegate[.]php  
  • http://163[.]123[.]143[.]4/download/YT_Client[.]exe 

Dropped executable file 

Title Description 
Name C:\Users\admin\AppData\Local\Microsoft\Windows\INetCache\IE\AH8CR9J5\YT_Client[1].exe 
SHA256 041f891934add72852c8fda245c95da959d7f98cc580383d198e42f2de039634 

DNS requests 

  • iplogger.org  
  • ipinfo.io  
  • Iplis.ru 

Connections (IP) 

  • “23[.]254.227.214” 
  • “23[.]254.227.202” 
  • “23[.]254.227.205” 
  •  “208[.]67.104.60” 







Malware analyst at ANY.RUN at ANY.RUN | + posts

I'm 21 years old and I work as a malware analyst for more than a year. I like finding out what kind of malware got on my computer. In my spare time I do sports and play video games.

Malware analyst at ANY.RUN
I'm 21 years old and I work as a malware analyst for more than a year. I like finding out what kind of malware got on my computer. In my spare time I do sports and play video games.

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