Grandoreiro Returns: The Banking Trojan Is Back, and Latin America Is Once Again in Its Crosshairs

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A Familiar Threat Reappears

Grandoreiro, one of Latin

According to research from

The numbers tell an important story. Grandoreiro may no longer be operating at the extraordinary levels seen during some of its previous campaigns, but it has clearly not disappeared. Instead, the malware ecosystem appears to have entered another phase of adaptation, using stealthier execution techniques and legitimate applications to make infection chains harder to identify.

Grandoreiro Refuses to Stay Down

Grandoreiro first became notorious for targeting users primarily across Latin America and later expanding its reach into countries such as Spain. The malware is designed around financial theft, making online banking customers particularly valuable targets.

The January 2024 law-enforcement operation disrupted important parts of the infrastructure associated with the malware. For a time, such interventions created expectations that Grandoreiro’s operators might have been significantly weakened.

But cybercrime rarely follows a simple beginning-and-end storyline.

When infrastructure is taken down, developers disappear, or distribution networks are interrupted, malware families can return through modified infrastructure, rebuilt campaigns, new loaders, and alternative distribution partners. Grandoreiro’s latest activity is another example of this resilience.

Mexico Emerges as the Main Target

The most striking geographic finding in the latest telemetry is Mexico’s 40% share of detected samples. Spain accounted for 17%, Peru for 13%, and Argentina for 10%.

This concentration reinforces

The Mexican concentration should therefore be viewed as more than a statistical curiosity. It may indicate that the current campaign has been deliberately optimized for victims in the country or that its distribution infrastructure is particularly effective there.

Legitimate Software Becomes the Trojan Horse

One of the most concerning elements of the campaign is Grandoreiro’s use of DLL sideloading.

Instead of simply launching a malicious executable and hoping security software does not notice, the attackers abused the trusted Duplicate Files Finder application. The legitimate executable was renamed and placed alongside a malicious mingwm10.dll file.

When the trusted program launched,

This technique is dangerous because the visible application can appear legitimate. The attacker does not necessarily need to disguise the entire program as something malicious. Instead, the trusted application becomes part of the execution chain.

Why DLL Sideloading Is So Effective

DLL sideloading takes advantage of a fundamental characteristic of many Windows applications: legitimate executables frequently load external dynamic-link libraries during startup.

If an attacker can place a malicious DLL in a location where the legitimate executable searches for its dependencies, the application may unintentionally execute the attacker’s code.

For defenders, this creates a difficult detection problem. Looking only at the executable’s reputation may not be enough.

Security teams need to examine relationships between executables, DLLs, file locations, signatures, parent-child processes, and unusual loading behavior.

The Malware Checks Its Environment First

Grandoreiro’s loader reportedly performs extensive anti-analysis checks before attempting to communicate with its command-and-control infrastructure.

That means the malware does not immediately reveal itself after execution.

Instead, it can inspect the environment for virtualization artifacts, sandbox indicators, security products, analysis utilities, system characteristics, and particular user or machine configurations.

This is an important defensive evolution.

Modern malware increasingly behaves like a suspicious employee who first looks around the room before speaking. If it believes the environment belongs to a researcher or automated security system, it may stop, change behavior, or avoid contacting its operators.

Virtual Machines Are No Longer Invisible

Security researchers routinely use virtual machines and sandboxes to analyze suspicious software. Malware developers know this.

As a result, modern malware families frequently inspect their surroundings for clues that they are running inside an analysis environment.

Grandoreiro’s reported checks demonstrate why malware analysis has become a constant contest between automation and evasion.

Attackers want their code to execute normally on a victim’s computer while behaving differently inside a research laboratory.

Defenders, meanwhile, must build analysis environments that resemble ordinary computers closely enough to prevent malware from recognizing them.

Geolocation Becomes Part of the Defense

The loader also reportedly checked the

This can provide attackers with another layer of filtering.

If a campaign is intended for specific countries, there is little reason for its operators to expose the complete malware chain to every computer on the internet. A sample can instead determine where the victim appears to be located and decide whether to continue.

Traffic from certain countries was reportedly blacklisted as well.

This approach can reduce unnecessary exposure and make automated research more difficult.

The Infection Vector Remains Unconfirmed

Acronis could not definitively establish how the malware initially reached victims.

However, the researchers noted an invoice-like ZIP filename and Grandoreiro’s historical distribution patterns. These clues led them to assess with moderate confidence that spam or malicious email distribution may have played a role.

That distinction matters.

Security researchers should separate confirmed observations from assessments based on historical behavior. The ZIP filename is evidence of a possible distribution strategy, but it does not by itself prove that email was the delivery mechanism.

This is an important lesson for anyone reading malware reports: confidence levels matter just as much as the headline.

Encrypted Strings Make Analysis Harder

The loader also used encrypted strings, adding another layer of difficulty for researchers.

Malware authors frequently encrypt or obfuscate strings to prevent analysts from immediately seeing URLs, commands, filenames, configuration values, or other useful information.

The technique does not make malware impossible to analyze, but it increases the amount of work required.

Analysts may need to execute the sample in a controlled environment, inspect memory, identify decryption routines, and reconstruct configuration data dynamically.

The Silent Command-and-Control Infrastructure

During

At first glance, an inactive server might appear to mean that the malware is no longer functional. But static examination suggested that the loader was designed to contact its C2 infrastructure and retrieve a second-stage payload after successfully completing its environmental checks.

That distinction is crucial.

A server being offline at the moment of research does not necessarily mean the malware campaign has ended. Infrastructure can be replaced, temporarily disabled, redirected, or reactivated.

The Two-Stage Payload Model

The apparent use of a second-stage payload also demonstrates how attackers can separate their initial infection mechanism from the final malware.

The first-stage loader can focus on execution, environmental checks, evasion, and communication.

Only after the victim passes those checks does the loader attempt to retrieve additional malicious components.

This architecture offers several advantages to attackers.

It reduces the amount of malicious functionality stored in the initial sample, allows operators to change later-stage payloads, and can make static detection more difficult.

Grandoreiro’s Geographic Footprint

The latest telemetry paints a clear regional picture.

Mexico represented 40% of detections, Spain 17%, Peru 13%, and Argentina 10%.

The remaining activity was distributed across smaller clusters in Latin America, Europe, and North America.

Although these figures represent detections rather than a definitive measurement of every infected machine, they provide a useful indication of where the campaign was most visible during the analyzed period.

Why Latin America Remains Attractive

Banking trojans have historically maintained strong interest in Latin America because financial services are an especially valuable target.

A successful banking trojan can attempt to steal credentials, monitor user activity, interfere with financial sessions, or provide attackers with information that can ultimately be monetized.

Grandoreiro’s continued focus on the region suggests that its operators still believe the potential financial return justifies rebuilding their infrastructure.

The 2024 Disruption Was Not the End

The most important conclusion from the latest research is not that Grandoreiro has returned.

It is that disruption and elimination are two different things.

The 2024 operation appears to have affected the malware’s infrastructure and activity, but the latest campaign demonstrates that parts of the ecosystem survived or were rebuilt.

This is a recurring pattern in cybercrime.

Taking down infrastructure can slow an operation dramatically, but long-term suppression often requires simultaneously targeting developers, distributors, infrastructure providers, financial channels, and other components of the criminal ecosystem.

Grandoreiro Is Evolving Rather Than Simply Returning

It would be misleading to describe the 2026 campaign as nothing more than a copy of older Grandoreiro operations.

The use of DLL sideloading, extensive environmental checks, geolocation filtering, encrypted strings, and staged payload retrieval demonstrates an ecosystem that continues to adapt.

The

Their response is to increase stealth, reduce unnecessary execution, and make the infection chain more dependent on legitimate components.

What This Means for Windows Users

For ordinary Windows users, the campaign is a reminder that trusted-looking software is not automatically safe when obtained from an untrusted source.

A legitimate

A familiar executable can become part of a malicious chain.

A ZIP archive can contain more than an innocent document.

And a file that appears to belong to a legitimate program may actually be a malicious DLL placed beside it.

Users should therefore avoid downloading software from unofficial websites, opening unexpected ZIP attachments, and running programs received through unsolicited emails.

What Businesses Should Learn

Organizations should treat this campaign as a detection engineering problem rather than simply an antivirus problem.

Endpoint security teams should monitor unusual executable/DLL relationships, suspicious files appearing beside legitimate applications, unsigned or unexpectedly signed libraries, unusual process trees, and outbound connections generated immediately after application startup.

Security teams should also correlate endpoint events with network telemetry.

A suspicious DLL alone may be difficult to classify. A suspicious DLL followed by an unexpected child process, geolocation request, and outbound connection is considerably more meaningful.

Deep Analysis

Understanding the DLL Sideloading Chain

A simplified version of the attack chain looks like this:

Legitimate executable → malicious DLL → loader → environment checks → C2 communication → second-stage payload

The key defensive question is not simply whether the executable is legitimate.

The question is: What does that executable load, where does it load it from, and what happens afterward?

Checking Suspicious DLL Files

On Windows, defenders can begin investigating suspicious DLLs with PowerShell:

Get-ChildItem "C:\Suspicious\Path" -Filter .dll |
Select-Object Name, Length, LastWriteTime

This is useful for identifying recently created or modified libraries near suspicious executables.

Checking Digital Signatures

A quick signature review can help identify files that do not match the expected software publisher:

Get-AuthenticodeSignature "C:\Suspicious\Path\mingwm10.dll"

An invalid, missing, or unexpected signature should not automatically be treated as proof of malware, but it deserves investigation.

Inspecting Running Processes

Defenders can examine active processes and their executable paths:

Get-Process |
Select-Object ProcessName, Id, Path |

Sort-Object ProcessName

For deeper enterprise investigations, endpoint detection and response platforms can provide process ancestry and module-loading telemetry that basic PowerShell cannot.

Looking for Recently Created Archives

Because the delivery mechanism was not conclusively established, defenders should also monitor suspicious ZIP archives arriving through email or downloaded from unusual locations.

A basic PowerShell search for recent ZIP files might look like:

Get-ChildItem "$env:USERPROFILE\Downloads" -Filter .zip |
Sort-Object LastWriteTime -Descending |
Select-Object -First 20 Name, FullName, LastWriteTime

This is an investigative command, not a Grandoreiro-specific detection rule.

Monitoring Outbound Connections

Network defenders should pay close attention to unusual connections made shortly after a suspicious application launches.

For a basic Windows inspection:

Get-NetTCPConnection -State Established |
Select-Object LocalAddress, LocalPort, RemoteAddress, RemotePort, OwningProcess

The process ID can then be correlated with the responsible application.

Hunting for DLL Sideloading

A stronger enterprise detection strategy should look for combinations of events:

Trusted executable

+

Unexpected DLL in application directory

+

DLL unsigned or incorrectly signed

+

Unusual child process

+

Unexpected outbound network connection

No individual indicator is guaranteed to identify Grandoreiro.

The value comes from the correlation.

What Security Teams Should Prioritize

Organizations should prioritize application directories that contain executable files alongside newly created DLLs.

They should investigate software that was renamed unexpectedly.

They should examine applications launched from user-writable directories.

They should review ZIP archives originating from suspicious or unexpected sources.

They should correlate unusual process execution with outbound connections.

They should investigate endpoint activity involving financial websites or credentials after suspicious software execution.

They should also make sure endpoint telemetry remains available long enough to reconstruct the complete infection chain.

What Undercode Say:

1.

The most important lesson here is that taking down infrastructure does not necessarily destroy an operation.

2. Malware Ecosystems Can Rebuild

Criminal groups can replace servers, modify loaders, change distribution methods, and continue operating.

3. The 2024 Operation Still Mattered

A disruption can reduce activity even if it does not permanently eliminate a malware family.

1. The Latest Activity Is Below Previous Peaks

That is an important distinction.

1. Lower Activity Does Not Mean Lower Risk

A smaller campaign can still cause serious damage to individual victims.

6. Mexico Deserves Particular Attention

With 40% of observed detections, Mexico is clearly the most prominent location in the latest telemetry.

7. Spain Remains Relevant

Spain’s 17% share also reflects Grandoreiro’s established expansion beyond Latin America.

1. DLL Sideloading Is the Most Technically Important Detail

The attackers are hiding malicious behavior behind legitimate software.

9. Trust Is Being Abused

The victim may see a recognizable application while the operating system is actually loading attacker-controlled code.

1. Security Teams Must Look Beyond File Reputation

A trusted executable can participate in a malicious execution chain.

11. Anti-Analysis Is Becoming Standard

Malware increasingly checks whether someone is watching.

12. Sandboxes Are Under Pressure

Automated analysis systems must continually improve their ability to resemble real user environments.

1. Geolocation Filtering Is Another Layer of Evasion

Attackers do not necessarily want every infected machine to receive the full payload.

14. Blacklisting Countries Can Reduce Exposure

It can also complicate security research and automated detection.

1. The Offline C2 Should Not Create False Confidence

Infrastructure can disappear temporarily and return later.

16. Second-Stage Payloads Increase Flexibility

Operators can modify later-stage malware without completely replacing the initial loader.

17. Encrypted Strings Increase Analysis Costs

Every additional layer of obfuscation slows down defenders.

18. The

That uncertainty should be preserved rather than replaced with speculation.

19. Invoice-Themed Archives Are Plausible Lures

Financial documents are psychologically effective because recipients often open them quickly.

20. Email Remains a Powerful Distribution Channel

Even sophisticated malware can benefit from simple social engineering.

21. Users Remain a Critical Security Boundary

Technology cannot completely compensate for every unsafe download or attachment.

1. Legitimate Software Can Become an Attack Vehicle

This is one of the most important lessons from the campaign.

1. Software Supply Chains Matter at the Endpoint Too

The danger is not limited to compromised package repositories.

1. File Placement Can Be an Attack Mechanism

Where a DLL is stored can determine whether a legitimate application loads it.

25. EDR Telemetry Becomes Extremely Valuable

Process ancestry and module-loading information can reveal relationships that antivirus signatures miss.

26. Network Visibility Complements Endpoint Visibility

The combination can expose the transition from local execution to C2 communication.

27. Financial Malware Deserves Special Attention

The potential impact goes beyond simply compromising a computer.

28. Organizations Should Protect High-Value Users

Employees handling banking, payments, accounting, and financial administration deserve additional monitoring.

29. Detection Should Be Behavioral

Security teams should hunt for suspicious combinations of actions rather than relying exclusively on malware names.

30. Reputation Alone Is Not Enough

A legitimate

31. Disruption Is Still Valuable

Even temporary interruptions can increase costs for attackers and reduce victimization.

1. But Disruption Must Be Followed by Intelligence

Understanding how operators rebuild is essential.

1. Grandoreiro Shows the Value of Long-Term Tracking

A malware family can disappear from headlines without actually disappearing.

34. Geographic Trends Can Help Defenders

Detection concentrations may reveal where campaigns are succeeding.

35. Security Researchers Should Track Infrastructure Changes

Domains, IP addresses, payloads, certificates, and delivery methods can change rapidly.

36. Defenders Should Expect Adaptation

Once one technique becomes detectable, attackers may move to another.

37. Windows Remains a Major Battleground

The enormous Windows software ecosystem gives attackers many opportunities to blend malicious activity with legitimate programs.

1. The Campaign Is a Reminder to Keep Software Sources Clean

Official vendors and trusted repositories remain preferable to random download sites.

39. Users Should Treat Unexpected Archives Carefully

A ZIP file can hide executables, scripts, DLLs, and other dangerous components.

1. Grandoreiro Is a Case Study in Malware Persistence

Its renewed activity demonstrates that modern cybercrime is not simply about creating malware—it is about maintaining an adaptable ecosystem.

✅ Grandoreiro Activity Was Observed Again in 2026

The supplied report states that

The telemetry discussed in the report indicates that the malware remained active despite earlier disruption efforts.

This supports the conclusion that Grandoreiro had not been permanently eliminated.

✅ Mexico Represented About 40% of Detected Samples

The reported telemetry places Mexico at approximately 40% of detections.

Spain followed with 17%, Peru with 13%, and Argentina with 10%.

These percentages describe analyzed detections and should not be interpreted as a precise measurement of all infections worldwide.

✅ DLL Sideloading Was Used

The campaign reportedly abused the legitimate Duplicate Files Finder application together with a malicious mingwm10.dll.

This is consistent with a DLL sideloading technique in which a legitimate executable is induced to load an attacker-controlled library.

The technique makes the legitimate executable part of a malicious execution chain.

✅ Anti-Analysis Techniques Were Present

The loader reportedly checked for virtualization, sandboxing, security tools, analysis utilities, system characteristics, and user or machine configurations.

It also checked public IP information and geolocation.

These behaviors are classic examples of malware attempting to identify whether it is running in a genuine victim environment or under investigation.

❌ The Initial Delivery Method Is Not Confirmed

The report does not establish with certainty that email was the initial infection vector.

An invoice-like ZIP filename and

Therefore, describing email as a confirmed delivery mechanism would go beyond the available evidence.

❌ The 2024 Disruption Did Not Permanently Destroy Grandoreiro

The renewed activity demonstrates that the malware ecosystem survived, returned, or was rebuilt.

However, that does not mean the 2024 operation was unsuccessful.

The report specifically indicates that current activity remained below the malware’s previous peak, suggesting that the disruption may still have had a meaningful impact.

Prediction

(+1) Grandoreiro Will Continue Adapting Its Delivery Techniques

Grandoreiro is likely to continue experimenting with trusted applications, DLL sideloading, staged payloads, geolocation filtering, and stronger anti-analysis mechanisms.

The malware’s survival after major infrastructure disruption suggests that its operators understand how to rebuild when portions of their ecosystem are removed.

Future campaigns may therefore become less dependent on easily recognizable malicious executables and increasingly rely on legitimate Windows applications as execution vehicles.

(+1) Behavioral Detection Will Become More Important

As attackers move away from obvious malware binaries, security vendors will increasingly focus on what software does rather than simply what software is.

Unusual DLL loading, suspicious application directories, abnormal process relationships, unexpected network connections, and strange execution paths will become increasingly valuable detection signals.

(+1) Latin America Will Remain an Important Target

Grandoreiro’s continued concentration in Latin America suggests that the region will remain attractive to operators seeking financial victims.

Mexico, in particular, deserves close monitoring given its dominant share of detections in the latest telemetry.

(-1) Infrastructure Takedowns Alone Are Unlikely to End the Threat

If the criminal ecosystem can replace infrastructure and modify its loaders, another isolated takedown may again produce only temporary results.

Long-term suppression will require coordinated action against the wider ecosystem supporting malware development, distribution, infrastructure, and monetization.

(+1) Grandoreiro’s Activity May Become Harder to Detect

The combination of anti-analysis checks, encrypted strings, geolocation filtering, legitimate software abuse, and staged payload delivery gives attackers multiple opportunities to remain below traditional detection thresholds.

That means defenders will need stronger endpoint telemetry, network correlation, threat intelligence, and behavioral analytics.

The Bigger Cybersecurity Lesson
Malware Does Not Need to Be Loud to Be Dangerous

Grandoreiro’s latest campaign is a reminder that modern malware does not always announce itself with obvious symptoms.

A victim may launch what appears to be a legitimate application.

The application may perform exactly what the user expects.

Meanwhile, a malicious DLL can execute quietly in the background, inspect the system, determine whether the machine is valuable, and attempt to contact attacker infrastructure.

The Real Battle Is About Trust

The most interesting part of this campaign is not simply the malware itself.

It is the abuse of trust.

Users trust familiar software.

Windows trusts applications to load required libraries.

Security systems trust known applications more than unknown binaries.

Attackers exploit those assumptions.

That is why Grandoreiro’s return matters. It demonstrates that the next generation of banking malware does not necessarily need to look malicious. Sometimes, it only needs to look legitimate long enough to get through the door.

Final Takeaway

Grandoreiro’s resurgence is another warning that malware disruption is rarely permanent. The 2024 law-enforcement operation appears to have damaged the threat’s infrastructure and reduced its overall activity, but the latest campaign demonstrates that the underlying operation remains capable of adaptation.

The use of DLL sideloading, legitimate software, encrypted strings, anti-analysis checks, geolocation filtering, and potential second-stage payload delivery shows how sophisticated modern banking malware has become.

For organizations, the lesson is clear: do not trust an executable simply because its name is familiar. Monitor how applications load DLLs, where those libraries come from, what processes they create, and where those processes communicate.

For users, the message is equally simple: unexpected ZIP files, invoice-themed attachments, unofficial software downloads, and unfamiliar installers deserve suspicion.

Grandoreiro may have been disrupted, but it was never truly forgotten. Its return shows that in cybersecurity, yesterday’s threat can quietly become tomorrow’s emergency—and the strongest defense is not waiting for the next headline, but understanding the attack chain before it reaches the victim.

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References:

Reported By: www.infosecurity-magazine.com
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