Unveiling Socks5Systemz: The Rise of a New Proxy Service via PrivateLoader and Amadey

socks5systemz blog hero

Key takeaways

  • Bitsight has uncovered a proxy botnet delivered by PrivateLoader and Amadey, two loaders frequently employed by threat actors to distribute malware and build their botnets. We've named this proxy bot malware Socks5Systemz, which is also the name associated with the unique login panel consistently present in all active proxy bot C2 servers.
  • While this proxy malware is not new (references on Twitter trace back to 2016), its usage must have remained under the radar, at least until now.
  • Upon researching and mapping the infrastructure behind this botnet, several servers associated with this malware operation were discovered, along with a Telegram user who has built a complete proxy service by leveraging this proxy botnet.
  • The proxy service allows clients to choose a subscription ranging from $1 USD to $4000 USD, payable in full using cryptocurrency.
  • Based on network telemetry analysis, it is estimated that this botnet has approximately 10.000 infected systems with victims spread across the globe.
  • No infected systems communicating with the backconnect servers were observed in Russia. This, combined with various other clues uncovered during the research (such as HTML comments, server error messages, etc.) allows us to assess with medium confidence that operators of the service are based in that geography.


Proxy services offer users the ability to rent a set of IP addresses for internet use, granting a level of online anonymity. Essentially, they make your internet traffic appear as if it's coming from a regular IP address while keeping the real origin hidden.

Recently, our Threat Research team discovered a new malware sample, distributed by the PrivateLoader and Amadey loaders. These two loaders are often used by threat actors to spread malware and build their armies of infected computers, also known as botnets.

This sample, upon reverse engineering, was found to install a proxy bot on infected systems, turning them into proxies capable of forwarding traffic for someone else. We've named this proxy bot Socks5Systemz, a name we found to be present on a login panel in all proxy bot C2 servers.

socks5systemz login page

Figure 1: Login page

In this blog post, we'll delve into how this proxy bot functions, explore its infrastructure, identify the victims, and uncover the proxy service built on top of this botnet. Let's get into the details.

Loader analysis

All samples delivered by PrivateLoader and Amadey dropped and executed a file named previewer.exe that we will refer to as just the loader from now on. This file is responsible for setting up the persistence and injecting the proxy bot in memory.

socks5systemz process tree

Figure 2: Process tree

This loader accepts three command line options:

Option Description


Creates empty file named "test" in the current directory and exit


Install loader


Start loader

The install option

The install option is responsible for setting up the persistence on the system and to do so it will try to copy the loader to C:\ProgramData\ContentDWSvc\ContentDWSvc.exe and create a Windows service to run the copied loader with both the name and display name set to ContentDWSvc.

socks5systemz service installation

Figure 3: Service installation

If file copy or service creation fails, the loader will try to kill all Google update processes and replace the GoogleUpdate.exe original executable by itself.

socks5systemz replacing google update executable

Figure 4: Replacing Google Update executable

The start option

This option will simply create a new thread to launch the loader main function and wait until it finishes.

socks5systemz main functio

Figure 5: Starting the loader main function

The loader main function will load the resource with ID 400 to memory and decrypt it. The decrypted data will be a valid DLL file containing the proxy bot that will be injected in memory.

socks5systemz decryption and injection of payload

Figure 6: Decryption and injection of payload

Proxy bot analysis

The proxy bot payload is a 32 bit DLL file with a size of ~300 KB. The entry point of the proxy bot saves the name of the current filename to a global variable, sets a global flag with the architecture of the system, and it creates a new thread to start the bot main function.

socks5systemz proxy bot entry

Figure 7: Proxy bot entry point

Next, the bot generates a 32-bit client ID based on the creation date of the Windows directory on the infected system.

On its initial run, the bot collects and stores the current system time (infection time) in a file named C:\ProgramData\ts.dat. Additionally, it fetches a PDF file from hxxp://datasheet[.]fun/manual/avon_4_2022.pdf?<client_id>, saving it in the C:\ProgramData folder.

socks5systemz downloading pdf

Image 8: Downloading PDF file from datasheet[.]fun

Despite the fact that the downloaded PDF doesn't contain any particularly interesting data and the domain is under the control of the threat actor, this step appears to be geared towards gathering extra telemetry and potentially aiding in the validation of infected systems.

socks5systemz pdf file content

Image 9: PDF file content

Finally, the bot tries to get the address of a C2 server that's online. To do so, the bot computes a domain name using a domain generation algorithm and uses a hardcoded list of DNS servers to resolve it.

socks5systemz hardcoded list dns resolvers

Figure 10: Hardcoded list of DNS resolvers

Since all DNS servers in the list are controlled by this threat actor, any domain that we try to resolve using them will point to a valid command and control server.

socks5systemz resolving a domain

Figure 11: Resolving a domain

​If the bot is unable to get a valid command and control server address using that method, it will send a HTTP GET request to bddns[.]cc to the following endpoint /sign/<rc4 data hex encoded>. The hex encoded data is the result of encrypting a string with the format <dga_domain>:<client_id_hex> using RC4 with the key heyfg645fdhwi. The response is also hex encoded and encrypted using the same RC4 key and contains the IP address of a valid command and control server.

socks5systemz requesting c2 address

Figure 12: Requesting C2 address from bddns[.]cc

After getting the IP address of an active command and control server, the bot is ready to start the C2 communications by doing a HTTP GET request to the following endpoint /single.php?c=<rc4 data hex encoded>.

socks5systemz bot request

Figure 13: Bot request

The data that goes in the c= parameter is the hex encoded result of encrypting the beacon string using the same RC4 key heyfg645fdhwi. The plain text beacon string has the following format: client_id=%.8x&connected=%d&server_port=%d&debug=%d&os=%d.%d.%04d&dgt=%d&dti=%d

Beacon Field Description



The client/bot ID hex



Status of backconnect connection (1 for connected and 0 for disconnected)


Port assigned to the bot by the backconnect server


Hardcoded value 17


Windows major, minor and build versions


Architecture (1 for 64 bit and 0 for 32 bit)


System time aka infection time

The responses from the command and control servers are also hex encoded and encrypted using the same RC4 key and they will contain commands for the bot.

socks5systemz bot request c2 response

Figure 14: Bot request and C2 response with idle command

Currently the bot supports the following commands:

Bot Command Description
idle Do nothing
connect Connect to a backconnect server
disconnect Disconnect from the backconnect server
updips Update IP addresses allowed to send traffic
upduris This command seems to not be fully implemented

The most important command is the connect command that tells the bot to establish a session with a backconnect server over port 1074/TCP. This command registers the bot with the backconnect infrastructure and makes it part of the pool of available proxies that can be used to send traffic on behalf of clients.

socks5systemz bot receiving command

Figure 15: Bot receiving a connect command

Connect command fields:

Connect Field Description
ip backconnect IP address
auth_swith authentication flag. If set to 0, the proxy will be available for the client IPs that come within the auth_ip field. If set to 1, the proxy clients will need to use the login and pass that comes within the auth_login and auth_pass fields.
auth_ip list of authorized IP addresses
auth_login login username for proxy
auth_pass login password for proxy
block list of ports that sending traffic is not allowed

After parsing all the connect command fields, the bot establishes a session with the backconnect server over port 1074/TCP using a custom binary protocol. Once the session is established, the bot can be used as a proxy.

socks5systemz backconnect communications proxy traffic

Figure 16: Backconnect communications with proxy traffic to google[.]com

When the bot establishes a session with a backconnect server through port 1074/TCP, it's assigned a unique TCP port (referred to as the server port) on the server side. This designated port is opened to receive traffic from clients. To use the proxy, clients need to know the backconnect server's IP address, the TCP port assigned to the infected system, and either have their public IP whitelisted or possess the appropriate login credentials. Without this information, the server will not accept the traffic.

socks5systemz client proxy overview

Figure 17: Overview on how the clients can use the proxies


At least 53 servers related to this botnet were identified, all located in Europe and distributed across France, Bulgaria, Netherlands, and Sweden.

socks5systemz geographic infrastructure
Figure 18: Infrastructure geographic distribution

The infrastructure is made up of servers with several purposes, which include:

  • Proxy bot C2 servers
  • Backconnect servers
  • Custom DNS servers (hardcoded in the proxy bot samples)
  • The server used by the bots to get the online C2 server address
  • A proxy checker application

Detailed infrastructure:

IP CC ASN Domain Description SE 42708, PORTLANE - Proxy bot C2 - Frontend BG 44901, BELCLOUD - Proxy bot C2 - Frontend NL 58329, RACKPLACE - Proxy bot C2 - Frontend NL 49981, WORLDSTREAM - Proxy bot C2 - Backend NL 49981, WORLDSTREAM - Proxy bot C2 - Backend not being used NL 49981, WORLDSTREAM, NL - Proxy bot C2 - Not deployed FR 16276, OVH - DNS server for DGA domains NL 49981, WORLDSTREAM - DNS server for DGA domains NL 49981, WORLDSTREAM - DNS server for DGA domains FR 16276, OVH - DNS server for DGA domains FR 12876, Online SAS - DNS server for DGA domains NL 49981, WORLDSTREAM bddns[.]cc Used to retrieve proxy bot c2
- - - datasheet[.]fun Telemetry server NL 49981, WORLDSTREAM - Backconnect FR 16276, OVH - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect FR 16276, OVH - Backconnect FR 16276, OVH - Backconnect FR 16276, OVH - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 12876, Online SAS - Backconnect FR 16276, OVH - Backconnect FR 16276, OVH - Backconnect FR 16276, OVH - Backconnect FR 12876, Online SAS - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect FR 16276, OVH - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect BG 44901, BELCLOUD - Backconnect FR 16276, OVH - Backconnect FR 16276, OVH - Backconnect NL 49981, WORLDSTREAM - Proxy checker app

The proxy service

During the investigation into the usage of the botnet infrastructure, an image separately surfaced on a Telegram channel. In this image, a user named boost shared a screenshot of an account checker tool utilizing the IP addresses of the backconnect servers as proxies. These IP addresses match the list derived through the aforementioned malware research, as shown in the previous section.

socks5systemz backconnect proxies

Figure 19: Backconnect proxies being used to check credentials

telegram boost user

Figure 20: Telegram user @boostanywork aka “boost”

It was discovered that boost is involved in selling compromised accounts and access to the proxies. Using a bot named BoostyProxy, the threat actor built a complete proxy service that allows users to subscribe to the service, manage the existing subscriptions, and access the current list of available proxies.

socks5systemz boost telegram bot

Figure 21: Telegram bot @BoostyProxy_BOT

socks5systemz boost telegram

Figure 22: Telegram bot chat

The service has two subscription options: standard and VIP. The difference between the two is that the standard only allows a client to use one type of proxy and does not support multithreading while the VIP subscription allows a client to send all types of proxy traffic (socks4, socks5, and http) and use multiple threads. Here’s the current price table for the two subscription options:

  • Standard proxy
Threads/Period 1 day 7 days 1 month 3 months
Single thread $1 USD $5.1 USD $10.3 USD $28 USD
  • VIP service
Threads/Period 1 day 5 day 10 day 1 month 3 months
100 threads $22 USD $60 USD $100 USD $175 USD $450 USD
300 threads $28 USD $68 USD $112 USD $200 USD $500 USD
500 threads $35 USD $90 USD $150 USD $300 USD $740 USD
1000 threads $42 USD $120 USD $200 USD $400 USD $1000 USD
5000 threads $140 USD $420 USD $700 USD $1500 USD $4000 USD

All payments must be done with crypto currency using the Cryptomus Crypto Payment Gateway (cryptomus[.]com).

While subscribing to the service, the client must provide the IP address from where it will access the proxies. Once the subscription process is complete, the client IP address gets whitelisted across the botnet, and clients can download the list of available proxies which contains the IP addresses of the backconnect servers and the TCP ports assigned to the infected systems.


Since PrivateLoader and Amadey loaders have been one of the main distribution channels for this proxy bot, we expected to see a pretty dispersed geographic distribution for the victims of this botnet, which was exactly what we observed on our network telemetry. Since the beginning of October, we observed approximately 10.000 systems communicating over port 1074/TCP with the backconnect servers.

The top 10 most affected countries are, in order, India, Brasil, Colombia, South Africa, Bangladesh, Argentina, Angola, United States, Suriname, and Nigeria.

socks5systemz effected countries

Figure 23: Geographic distribution of victims

Due to the nature of this network telemetry, these numbers must be interpreted as an approximation of what can be the real botnet size and geographic distribution of the victims.


(For network indicators, please refer to the table shared in the “Infrastructure” section.)

Socks5Systemz proxy bot payload


Proxy bot loader payload


Packed files distributed by Amadey and PrivateLoader

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