# PrivateLoader: Analyzing the Encryption and Decryption of a Modern Loader

**[any.run/cybersecurity-blog/privateloader-analyzing-the-encryption-and-decryption-of-a-modern-loader/](https://any.run/cybersecurity-blog/privateloader-analyzing-the-encryption-and-decryption-of-a-modern-loader/)**

khr0x April 18, 2023

[HomeMalware Analysis](https://any.run/cybersecurity-blog/)
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


## 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


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**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

```

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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.](https://any.run/?utm_source=anyrunblog&utm_medium=article&utm_campaign=privateloader&utm_content=landing)

Here’s a link to the task:

[https://app.any.run/tasks/3e359dc7-934b-4ae1-89bf-ad33e346ed60](https://app.any.run/tasks/3e359dc7-934b-4ae1-89bf-ad33e346ed60?utm_source=anyrunblog&utm_medium=article&utm_campaign=privateloader&utm_content=task)

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


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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.


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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):


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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:

data=kSYhy9HPjD5Jhn9y6Evty4XFfJ3JgIwrSzln5bGnLfKDmbXix2ebDEXy6Ty3Bb8Hz2GB8w0Y2SL2JeBSZ4G80iHAkSS7JJyeiPwZOpWJONOFzEBar
ljR9hkvX_TJhqr1nNqQpYUB2lQ9i7NmmHeL_QSx8hUka_C3jOxi02ml5FyDDruXM_IWwPXvAGxtT8TVi9wLtfd0mF1O369GUAEeI45sF1pKeyDfssmqE=

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


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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:


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PrivateLoader data


Fig. 7 – Data

1. Loading the encryption key into the stack:


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Key PrivateLoader


Fig. 8 – Key

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


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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.


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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](https://github.com/JonathanSalwan/Triton)
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](https://github.com/anyrun/blog-scripts/blob/main/Extractors/Privateloader/PrivateLoader.py?utm_source=anyrunblog&utm_medium=article&utm_campaign=privateloader&utm_content=script)
server.


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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:


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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.

## Conclusion

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](https://any.run/cybersecurity-blog/limerat-malware-analysis/)
process of XLoader/FormBook.

## MITRE (ARMATTACK)

**Tactics** **Techniques** **Description**


TA0007:

Software discovery


T1518:

Software Discovery

T1082:

System Information

Discovery


Searches for installed software

in the system

in the “Uninstall” key

Collects system data


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TA0011:

Command and Control


T1071.001:

Application Layer

Protocol


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

## IOCs

**Title** **Description**


abuse the Windows Task

Scheduler to create file in statup


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”

## MORE SAMPLES FOR YOUR RESEARCH


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ttps //app a y u /tas s/ 8 [a6 6c](https://app.any.run/tasks/ff1872a6-6c1f-4f79-89da-995b9bd56152/) 9 89da 995b9bd56 5 /

[https://app.any.run/tasks/6a8f93eb-be36-41bc-bf7f-534938a7e3a2/](https://app.any.run/tasks/6a8f93eb-be36-41bc-bf7f-534938a7e3a2/)

[https://app.any.run/tasks/cc2cb367-82e9-4705-9767-8c12f7a67a21/](https://app.any.run/tasks/cc2cb367-82e9-4705-9767-8c12f7a67a21/)

[https://app.any.run/tasks/c32312d8-4026-4a81-84e5-3d90ab2e309a/](https://app.any.run/tasks/c32312d8-4026-4a81-84e5-3d90ab2e309a/)

[https://app.any.run/tasks/235754fa-6aa3-49dd-bbc4-1a7f9361f455/](https://app.any.run/tasks/235754fa-6aa3-49dd-bbc4-1a7f9361f455/)

ANY.RUN
malware analyst


khr0x

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.

User avatar
khr0x
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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