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GoSecure
Archived: 2026-04-05 16:45:06 UTC
Preface
Our Inbox Detection and Response (IDR) team has observed a new BazarLoader campaign targeting the information
technology, aeronautic and financial industries. The IDR team has successfully blocked over 550 thousand BazarLoader
malspam emails throughout this campaign alone.
GoSecure researchers received a sample from the IDR team which was suspected of being BazarLoader, named Report
Preview15-10.exe, on 2020-10-06. Shortly after, GoSecure researchers received yet another BazarLoader sample on 2020-
10-08 named Document2-85.exe, which exhibited similar behavior.
Analysis
The initial infection vector, which has been observed by our Inbox Detection and Response Team (IDR), is via malspam
containing fake employment termination notices and anonymous surveys. The threat actor(s) primarily use Google Drive
and Google Docs to distribute their malicious payloads. The employment termination malspam was observed on October 6,
2020 and the anonymous survey malspam was observed on October 8, 2020. This can be seen in Figure 1 and Figure 2.
Figure 1: BazarLoader Employment Termination Malspam
Figure 2: BazarLoader Fake Anonymous Survey
We will firstly analyze the employment termination malspam.
Once the user clicks the link, they will be redirected to
hxxps://docs[.]google[.]com/document/d/e/2PACX-1vR_9tGGWDcS1ZyIuiGpMQg2Sv9nRWempyUKuQ1iyJp_HHt1C87OPirnO7EImnOW6ILbrmHXUpl_OIxQ/pub to
download an executable.
The executable Review_Report15-10.exe (3c27fca6d9cf1379eee93e6fea339e61) will appear as a
PDF document to users who do not have extensions enabled in Windows, as seen in Figure 3.
Figure 3: Stage 1 PDF Icon Lure
To help obfuscate its purpose, BazarLoader appears to be bound or obfuscated with legitimate resources from YUVPlayer (A
Lightweight YUV player which supports various YUV formats). An example of this can be seen in Figure 4.
Figure 4: YUVPlayer Dialog Embedded Resource
Once executed, the legitimate application or dialogs will not be shown to the user. Instead, it will call
advapi32.CryptHashData using the string s_)q03vcOm95^+Rj3dG_Jx@k0GGwYOIddH_14025b520 as the data to create a hash
using the PROV_RSA_FULL Windows cryptographic provider. Once the hash is created, it will create a key using
advapi32.CryptDeriveKey . It will then obtain a handle to the current process for the purpose of allocating memory with
PAGE_EXECUTE_READWRITE permissions. The next function is responsible for copying the shellcode from the .data section
to the newly allocated memory location. Once the encrypted shellcode has been copied to executable memory, it will then
use advapi32.CryptEncrypt to decrypt the shellcode. Once the shellcode has been successfully decrypted, it will execute
the shellcode.
Figure 5: BazarLoader Shellcode Decryption Routine
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Figure 6: Executing Stage 1 Decrypted Shellcode
The shellcode will obtain a handle to kernel32.LoadLibraryA , kernel32.GetProcAddress , kernel32.VirtualAlloc ,
kernel32.VirtualProtect and ntdll.ZwFlushInstructionCache , by enumerating the Process Environment Block (PEB)
using the instruction mov rax,qword ptr gs: [60] . This is common with shellcode as it will need to resolve these APIs
dynamically to interact with the Windows operating system.
Once completed, it will then call kernel32.VirtualALloc to prepare injecting a PE executable for the next stage. To build
the PE header, it will use the routine shown in Figure 7.
Figure 7: Prepare Stage 2 PE
Once PE header has been partially copied (excluding MZ magic value), it will start to copy the .text section using the
routine shown in Figure 8.
Figure 8: Copy .text Section
Once the .text section is copied, it will start resolving many different Windows APIs using kernel32.GetProcAddress .
When the additional APIs have been resolved, it will then make the .text section it copied earlier executable using
kernel32.VirtualProtect , as seen in Figure 9.
Figure 9: Make .text Section Executable
NOTE: *On different debugging sessions the virtual addressing changed during analysis. *
Interestingly, the Portable Executable (PE) BazarLoader is copied into memory (without the MZ
header) and will start execution at the end of the .text section using a direct call . This can make unpacking the next
stage confusing for reverse engineers as this is not where code in a PE file is supposed to begin. This code at the end of the
.text section is solely responsible for making a call to the real Original Entrypoint (OEP) of the PE. It is important to note
that this is simply used as shellcode and not as a PE in memory. The other benefit of this technique is no calls to thread
related APIs are required, making it more challenging for Endpoint Detection and Response (EDR) solutions to detect. This
can be seen in Figure 10.
Figure 10: OEP Shellcode/PE Trickery
After the previous trickery in the new memory space, it will start creating another PE in memory, but this time the header
does start with the MZ magic value. After building the headers, it will copy each PE section one at a time, as seen in Figure
11.
Figure 11: Building .text Section for Stage 2
Once the PE has been extracted to memory, it will make a direct call instead of using Threading APIs (same trickery as
before). This can be seen in Figure 12.
Figure 12: Calling Stage 2 Shellcode
BazarLoader's stage 2 shellcode will make use of encrypted stack strings for many purposes
throughout the rest of its code.
Before it continues with its malicious activity, it will check if the locale is Armenian (0x2b). Interestingly, instead of shutting
down gracefully when the Armenian locale is detected, it will execute a jmp instruction to an invalid address, causing an
access violation exception. We have seen Russian crimeware checking for the Armenian keyboard layout previously in
malware such as KPot, we hypothesize this could be similar behavior.
To avoid running more than one instance of itself, BazarLoader will create a mutex with a hard-coded UUID, then use
kernel32.GetLastError to check for the error ERROR_ALREADY_EXISTS . If the mutex already exists, it will exit the process.
The call to kernel32.CreateMutexA can be seen in Figure 13.
Figure 13: Mutex Creation
Interestingly, BazarLoader will check for mutexes twice.
Once completed, it will decyrpt its C2 configuration, as seen in Figure 14.
Figure 14: BazarLoader Stage 2 Decrypted Downloader ConfigOnce BazarLoader has determined the Armenian language is
not being used and another instance of itself is not running, it will make a HTTP HEAD request to hxxps://titlecs[.]com. It
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will continue to do this until it receives a 200 response from the C2 server. The first request will be sent using
wininet.HttpSendRequestA , as seen in Figure 15.Figure 15: HTTP HEAD RequestIt is important to note that the HTTP
header Update is not a standard header and can be considered anomalous.
This HEAD request can be seen in Figure 16.Figure 16: BazarLoader C2 Download Domain HEAD Request
The C2 server will respond with a 200 OK message.
BazarLoader will also check if it is connected to the internet by making a request to microsoft[.]com, as seen in Figure 17.
Figure 17: BazarLoader Internet Connectivity Check
Once completed, it will make a POST request to the second domain in its configuration, as seen in Figure 18.
Figure 18: BazarLoader C2 Checkin
Once completed, it will make a HTTP GET request in order to obtain the next stage, as seen in Figure 19.
Figure 19: BazarLoader Downloading Encrypted Payload
Differences Between Versions
There are a few notable differences between the first version of BazarLoader sent on 2020-10-06 (Employment Termination
Malspam) and the one sent on 2020-10-08 (Survey Malspam). The main difference between the two versions is the malware
author(s) now include the string Stupid Defender to mock researchers, the shellcode that was stored in the .data section is
now stored in the .rsc section, the functionality to get a pointer to the encrypted shellcode and to decrypt it have been
broken out into their own separate functions. This can be seen in Figures 20 and 21.
Figure 20: Updated Main Shellcode Decryption/Execution RoutineFigure 21: Obtain Encrypted Pointer to Encrypted
Shellcode from the Resource SectionFigure 22: Encrypted Shellcode in Resource Section
Summary
BazarLoader is becoming increasingly popular amongst threat actors. We suspect the reason behind the malware
developer(s) success is their use of techniques such as avoiding the use of threading APIs and faking PE injection, when in
reality, it is simply shellcode injection. These techniques are likely used to confuse Endpoint Detection and Response (EDR)
solutions.
[/et_
pb_row]
Indicators of Compromise
**Indicator** **Description
hxxps://titlecs[.]com/issues/284
BazarLoader
Encrypted
Payload URL
hxxps://titlecs[.]com/issues/282
BazarLoader
Encrypted
Payload URL
hxxp://ds46x1[.]com/1/run
BazarLoader
Encrypted
Payload URL
labelcs[.]com BazarLoader
Domain
(Employment
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Termination
Malspam)
mixcinc[.]com
BazarLoader
Domain
(Employment
Termination
Malspam)
nicknamec[.]com
BazarLoader
Domain
(Employment
Termination
Malspam)
3c27fca6d9cf1379eee93e6fea339e61
BazarLoader
Shellcode
Injector
(Preview15-
10.exe)
3ee60e0efeb5b349a5ba7325ce4a33dc
BazarLoader
Shellcode
Injector
(Document2-
85.exe)
hxxps://docs[.]google[.]com/document/d/e/2PACX-1vR_9tGGWDcS1ZyIuiGpMQg2Sv9nRWempyUKuQ1iyJp_HHt1C87OPirnO7EImnOW6ILbrmHXUpl_OIxQ/p
Employment
Termination
Malspam
Payload URL
hxxps://docs[.]google[.]com/document/d/e/2PACX-1vQ7wK9C0fLCwS3voYLhGz3Gmy6g4UMKe_xZ1ds8xv7LonpviJBXefG9rBZuMPkmtytDYe_5rbDztBnK/pub
Survey
Malspam
Payload URL
ds45x1[.]com
BazarLoader
Domain (Surv
Malspam)
ds46x1[.]com
BazarLoader
Domain (Surv
Malspam)
ds47x1[.]com
BazarLoader
Domain (Surv
Malspam)
marcene[.]jack[at]peytoneley[.]com
BazarLoader
Malspam Em
shannon[.]ong35[at]myhunter[.]cuny[.]edu BazarLoader Malspam
BazarLoader
Malspam Em
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bessie[.]wilson[at]griply[.]com
BazarLoader
Malspam Em
## Researchers
Lilly Chalupowski
Paul Neuman
Source: https://www.gosecure.net/blog/2021/02/01/bazarloader-mocks-researchers-in-december-2020-malspam-campaign/
https://www.gosecure.net/blog/2021/02/01/bazarloader-mocks-researchers-in-december-2020-malspam-campaign/
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