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A Familiar Threat Returns With a More Dangerous Face
Grandoreiro was never supposed to disappear quietly. After years of stealing banking credentials across Latin America and expanding into markets around the world, the notorious banking Trojan faced a major setback in 2024 when Brazilian and Spanish authorities, assisted by Interpol, disrupted parts of its infrastructure and arrested five alleged administrators.
For a while, the criminal operation appeared significantly weakened.
But malware rarely follows the clean ending that defenders hope for.
A new campaign targeting users in Mexico shows that Grandoreiro remains active and, more importantly, that its operators are refining the techniques used to hide the malware from security products and researchers. The campaign combines malicious code with legitimate software, deceptive invoice archives, DLL sideloading, environment checks, and extensive anti-analysis mechanisms.
The result is not simply an old banking Trojan returning to the battlefield. It is an example of how a mature cybercrime operation can survive disruption by changing its tools, infrastructure, and delivery methods.
The Mexico Campaign Reveals a Resilient Criminal Ecosystem
Security researchers at Acronis identified the latest activity primarily affecting users in Mexico, while telemetry also showed a smaller number of victims in North America and Europe.
The geographical pattern remains important.
Grandoreiro has historically concentrated on Spanish- and Portuguese-speaking markets, particularly Latin America. Mexico therefore fits naturally into the Trojan’s established targeting strategy, even though infections outside the region demonstrate that the campaign can reach much farther.
The new activity also illustrates an uncomfortable reality for financial institutions: taking down infrastructure or arresting operators can disrupt a malware family without necessarily destroying the ecosystem that supports it.
From Brazilian Banking Trojan to Global Financial Threat
Grandoreiro first appeared around 2016 and was initially associated strongly with Brazil.
The malware was reportedly developed in Delphi and is believed to have originated with Brazilian Portuguese-speaking cybercriminals. Over time, however, its ambitions grew.
Instead of remaining a Brazil-focused threat, Grandoreiro expanded into other Latin American countries and eventually appeared across multiple continents.
By 2024, IBM researchers had observed campaigns targeting customers of more than 1,500 banks in over 60 countries spanning South and Central America, Europe, Africa, and the Indo-Pacific region.
That scale suggested that Grandoreiro was no longer just a small regional banking Trojan.
It had become part of a broader criminal business model.
The Malware-as-a-Service Problem
One of the most concerning characteristics of Grandoreiro has been the possibility that it operates as malware-as-a-service, or MaaS.
A MaaS model changes the economics of cybercrime.
Instead of one criminal group having to perform every stage of an attack, different actors can specialize in development, infrastructure, distribution, access, credential theft, or monetization.
This creates redundancy.
If one group is arrested, another participant may still possess access to the tools, infrastructure, source code, or operational knowledge necessary to continue attacks.
That helps explain why disruption does not always equal eradication.
Thousands of Banks in the Crosshairs
Kaspersky separately estimated that Grandoreiro activity involved around 1,700 targeted banks across 45 countries during the same period.
The numbers differ because cybersecurity companies observe different portions of criminal campaigns and use different methodologies for measuring targeting.
Nevertheless, both assessments point toward the same conclusion.
Grandoreiro became a serious international banking threat rather than a narrowly localized Brazilian malware family.
What Grandoreiro Wants From Victims
At its core, Grandoreiro is designed to attack financial information.
Banking credentials remain one of its most valuable targets because stolen usernames, passwords, authentication information, and session data can potentially be converted into direct financial theft.
But credential theft is only part of the danger.
Grandoreiro has also been associated with capabilities such as keystroke logging, screen sharing, and remote interaction with compromised machines.
This gives attackers a much broader view of a victim’s activity.
A stolen password is useful.
A compromised computer that allows criminals to observe how a victim logs into a financial service can be considerably more valuable.
The Attack Begins With an Invoice
The newest Mexican campaign reportedly begins with a ZIP archive disguised as an invoice.
That is an intentionally mundane lure.
Invoices are common in business environments. Employees regularly receive attachments containing bills, purchase confirmations, payment requests, XML documents, and PDFs.
An attacker does not necessarily need an exotic social-engineering story when the attachment itself looks like ordinary business paperwork.
The malicious archive reportedly contains PDF and XML documents designed to make the package appear legitimate.
These files function as decoys.
The Legitimate Application Becomes the Weapon
One of the most interesting aspects of this campaign is the use of Duplicate Files Finder, a legitimate file-management application.
The software itself is not inherently malicious.
That distinction matters.
Cybercriminals increasingly abuse trusted applications because security systems often have more difficulty treating a familiar executable as inherently suspicious.
The attackers modify or package the legitimate application in a way that allows it to load malicious code.
This is where DLL sideloading enters the attack chain.
DLL Sideloading Explained
DLL sideloading occurs when attackers exploit the way a legitimate Windows application searches for and loads dynamic-link libraries.
Instead of directly executing a suspicious malware executable, the attacker places a malicious DLL where a legitimate program will load it.
The legitimate program becomes the launcher.
This can complicate detection because the visible process may appear to belong to trusted software.
The technique has been used by numerous malware families for years, but its continued popularity demonstrates something important: old techniques remain effective when they are combined with modern evasion.
The Loader Does Not Immediately Reveal Its Intent
The Grandoreiro loader reportedly performs extensive checks before communicating with its command-and-control infrastructure.
This behavior is designed to answer a critical question:
Am I running on a real
That question has become increasingly important for modern malware.
Automated malware-analysis systems frequently execute suspicious files inside virtual machines and sandboxes.
If malware detects those environments, it can simply refuse to execute.
Grandoreiro Checks the Environment
According to Acronis, the loader examines numerous characteristics of the infected machine.
These include system uptime.
It checks available memory.
It looks at processor information.
It examines disk space.
It evaluates screen resolution.
It monitors signs of recent user activity.
It also searches for combinations of installed applications that may indicate a sandbox or analysis environment.
The malware reportedly checks for applications including Chrome, Firefox, CCleaner, and Microsoft Edge-related components.
The objective is not necessarily to find one specific program.
Instead, the combination of several environmental signals can help the malware estimate whether it is operating on a normal consumer or business system.
Nearly 50 Security and Analysis Tools
The loader reportedly searches for nearly 50 security, debugging, reverse-engineering, and network-monitoring tools.
That is a significant development because it demonstrates that the attackers are not merely trying to evade traditional antivirus software.
They are attempting to evade the entire analysis process.
Security researchers frequently rely on debuggers, reverse-engineering platforms, packet-analysis utilities, monitoring software, and specialized malware-analysis environments.
Grandoreiro’s loader attempts to identify signs of those tools before revealing its full behavior.
The Malware Waits Before Calling Home
The loader reportedly performs its checks before establishing communication with the command-and-control server.
This sequencing is strategically important.
If the malware immediately connects to a C2 server, analysts can capture the network traffic and investigate the infrastructure.
But if the loader first decides whether the environment looks genuine, it can avoid making that connection inside a laboratory.
That creates a frustrating problem for defenders.
The malware may appear dormant during analysis while behaving aggressively on a real victim’s machine.
Anti-Forensics Changes the Investigation
Anti-analysis is designed to prevent researchers from understanding malware.
Anti-forensics goes a step further.
The objective is to make evidence harder to collect, interpret, or preserve.
For defenders, this can increase the time required to determine what happened during an intrusion.
Every additional hour spent understanding an attack can give criminals more time to maintain access, steal information, or move toward financial theft.
That is why seemingly small changes to a loader can have a major operational impact.
A New Separation Between Access and Payload
Perhaps the most significant strategic clue in the campaign is the apparent separation between the initial loader and the main Grandoreiro payload.
The loader does not necessarily need to contain everything required for the attack.
Instead, it can act as a gatekeeper.
First, it determines whether the environment looks suitable.
Then it contacts the C2 infrastructure.
Only afterward does it retrieve the main payload.
This modular approach makes the campaign easier for criminals to modify.
If defenders discover one component, attackers can potentially replace that component without rebuilding the entire operation.
Why This Matters More Than the
Grandoreiro is approximately a decade old.
That might make it tempting to describe the malware as outdated.
That would be a mistake.
The age of a malware family is much less important than the speed at which its operators adapt.
An old malware family using new delivery methods, stronger evasion, updated infrastructure, and improved operational security can remain highly dangerous.
Cybersecurity history is filled with malware families that survived far longer than defenders expected.
Law Enforcement Disruption Is Still Valuable
The resurgence does not mean the 2024 law-enforcement operation failed.
Quite the opposite.
Disruption can reduce an
The evidence described by Acronis reportedly indicates that Grandoreiro’s activity is lower than its previous peak.
That matters.
But disruption is not the same as permanent elimination.
Cybercriminal groups can rebuild.
The Criminal Business Model Is the Bigger Threat
Grandoreiro should therefore be viewed as more than one executable file.
It is better understood as an ecosystem involving malware development, distribution, phishing infrastructure, command-and-control systems, compromised hosts, financial targets, and criminal monetization.
Destroying one component can damage the ecosystem.
Destroying every component is considerably harder.
This is why international cooperation remains essential.
Mexico Is an Important Warning
The Mexican campaign provides a useful warning to financial institutions throughout Latin America.
Attackers do not need a revolutionary exploit to cause damage.
They can combine ordinary phishing with legitimate software and well-established Windows techniques.
The sophistication comes from how those pieces are assembled.
An invoice lure.
A compressed archive.
A legitimate application.
A malicious DLL.
Environment detection.
Anti-analysis checks.
C2 communication.
Payload retrieval.
Each individual component may appear manageable.
Together, they form a highly effective attack chain.
The Human Element Remains Critical
Even the most sophisticated loader often requires an initial opportunity.
That opportunity may come from a user opening an attachment, extracting an archive, launching an unexpected executable, or trusting a document that appears to come from a supplier or financial partner.
Technology cannot completely eliminate that risk.
Organizations should therefore combine endpoint security with email filtering, attachment sandboxing, application controls, user awareness, and network monitoring.
No single security product should be expected to stop the entire chain.
Deep Analysis: Understanding the Grandoreiro Attack Chain
Stage One: Delivery
The campaign reportedly begins with a ZIP archive disguised as an invoice.
Defenders should pay particular attention to unexpected compressed attachments and invoice-related messages originating outside established business relationships.
Stage Two: Decoy Documents
The archive reportedly contains PDF and XML documents designed to create a sense of legitimacy.
The presence of a document does not automatically make an archive safe.
Security teams should examine the complete archive contents rather than focusing only on the visible file.
Stage Three: Trusted Application Abuse
The attackers use a legitimate file-management application as part of the loading process.
This demonstrates why executable allowlisting based purely on application names is insufficient.
Stage Four: DLL Sideloading
The legitimate executable is used to load a malicious DLL.
For defenders investigating suspicious Windows activity, process-to-DLL relationships can therefore provide important evidence.
Stage Five: Environment Detection
The loader checks system characteristics and searches for security and analysis tools.
A suspicious process that performs extensive system enumeration immediately after an archive-based execution deserves investigation.
Stage Six: C2 Communication
If the environment appears suitable, the loader communicates with its command-and-control infrastructure.
Network monitoring can therefore become an important second line of defense.
Useful Windows Investigation Commands
Security teams investigating a suspected endpoint can begin with basic Windows process and network inspection commands:
Get-Process | Sort-Object CPU -Descending
Inspect Active Network Connections
Get-NetTCPConnection | Where-Object {$_.State -eq "Established"}
Examine Recently Running Processes
Get-CimInstance Win32_Process | Select-Object ProcessId, ParentProcessId, Name, CommandLine
Search for Suspicious DLL Relationships
Get-Process | ForEach-Object {
try {
$_.Modules | Select-Object ModuleName, FileName
} catch {}
}
Check Windows Event Logs
Get-WinEvent -LogName Security -MaxEvents 100
Search for Recently Created Executables
Get-ChildItem "$env:TEMP","$env:APPDATA" -Recurse -File -ErrorAction SilentlyContinue |
Where-Object {$_.Extension -in ".exe",".dll",".zip"} |
Sort-Object LastWriteTime -Descending |
Select-Object -First 50 FullName, LastWriteTime
Network-Level Detection
Security teams should monitor endpoints for unexpected outbound connections immediately following execution of unfamiliar archive contents.
DNS monitoring, proxy logs, endpoint telemetry, and firewall records can help identify the infrastructure contacted by a compromised host.
Important Defensive Principle
These commands are useful for investigation, but they should not be treated as a complete Grandoreiro detection system.
A sophisticated loader can change filenames, paths, network infrastructure, and execution behavior.
Behavioral detection is therefore more valuable than relying on one static indicator.
What Undercode Say:
Evolution Beats Age
Grandoreiro’s most important characteristic today is not that it survived.
It is that it learned.
Disruption Creates Pressure
Law enforcement forced the operators to change their infrastructure and operational methods.
That pressure appears to have encouraged a stronger emphasis on stealth.
The Loader Is Becoming the Battlefield
The latest campaign demonstrates that attackers increasingly understand that the first-stage loader can determine whether an entire operation succeeds.
Detection Is Becoming a Game of Behavior
Traditional signatures remain useful, but they are increasingly insufficient against loaders designed to recognize analysis environments.
Legitimate Software Creates Ambiguity
Using trusted applications gives attackers an opportunity to blend malicious behavior into processes that security teams might not immediately consider suspicious.
DLL Sideloading Remains Relevant
The continued use of DLL sideloading proves that attackers do not need brand-new techniques when established ones remain effective.
Phishing Still Works
Despite years of security education, malicious attachments remain one of the most reliable ways to obtain an initial foothold.
Financial Malware Has a Direct Business Model
Unlike some espionage campaigns, banking Trojans have an obvious financial objective.
Every compromised account can potentially become a revenue opportunity.
Latin America Remains a Major Target
Mexico’s appearance in this campaign reinforces the importance of regional threat intelligence.
Language Can Influence Targeting
Grandoreiro’s historical focus on Spanish- and Portuguese-speaking populations gives defenders useful context when prioritizing suspicious campaigns.
Geographic Concentration Is Not Geographic Containment
Even when most victims are concentrated in Latin America, infections can still appear in Europe and North America.
Malware Does Not Respect Borders
Digital infrastructure allows criminals to operate across multiple jurisdictions simultaneously.
International Cooperation Is Essential
The 2024 disruption demonstrated the value of coordinated law enforcement.
The new campaign demonstrates why that cooperation must continue.
Malware Families Can Survive Their Developers
Source code, infrastructure knowledge, operational techniques, and criminal partnerships can survive arrests.
Arrests Do Not Automatically Destroy Demand
As long as financial credentials have criminal value, attackers will continue looking for ways to steal them.
Modular Malware Is Harder to Defeat
Separating loaders from payloads allows criminals to change individual components more easily.
Anti-Sandbox Technology Creates an Arms Race
Every new evasion technique pushes defenders toward more realistic analysis environments.
Analysts Must Think Like Attackers
Understanding what malware expects to find on a victim machine can reveal why automated analysis sometimes misses malicious behavior.
Endpoint Telemetry Becomes Crucial
Security teams need visibility into process creation, DLL loading, network activity, and unusual system discovery.
Email Security Cannot Work Alone
Blocking malicious attachments is valuable, but it cannot compensate for weak endpoint controls.
Application Control Deserves More Attention
Organizations should consider restricting which applications can execute from temporary or user-writable locations.
Least Privilege Can Reduce Damage
A compromised standard user account generally provides fewer opportunities than an account with unnecessary administrative privileges.
Banking Customers Need Strong Authentication
Passwords alone remain attractive targets for credential-stealing malware.
Financial Institutions Need Fraud Detection
Cybersecurity does not end at the endpoint.
Banks should also monitor suspicious transaction behavior that may follow account compromise.
Detection Should Focus on the Entire Chain
A single alert may look harmless.
A sequence of archive extraction, unusual application execution, DLL loading, system enumeration, and unexpected outbound traffic is far more suspicious.
The Attack Chain Leaves Clues
Even stealthy malware must interact with the operating system.
Those interactions create telemetry.
Security Teams Should Hunt for Relationships
Process ancestry can be more informative than filenames.
Network timing can be more useful than a static IP address.
Behavior can reveal what signatures miss.
Grandoreiro Is a Warning for Other Malware Families
The techniques described here are not exclusive to one Trojan.
Other criminal groups can copy them.
Todays Evasion Becomes Tomorrows Standard
Once an anti-analysis technique proves successful, it can spread quickly through underground malware development communities.
Security Vendors Face a Moving Target
Threat intelligence must continuously adapt because the same malware family can change its behavior without changing its overall mission.
The Biggest Mistake Is Assuming the Threat Is Gone
Grandoreiro’s reduced activity after disruption could easily have encouraged organizations to lower their defenses.
That would be precisely the wrong lesson.
Resurgence Does Not Mean Defeat
The current campaign appears smaller than
That means defensive pressure has achieved something.
But Reduced Scale Can Hide Improved Quality
A smaller operation with stronger evasion may still produce serious damage.
Financial Malware Will Keep Evolving
Criminals have powerful economic incentives to improve credential theft.
Security Awareness Must Evolve Too
Employees should be taught to question unexpected invoices, compressed attachments, and requests to open unfamiliar files.
The Long-Term Battle Is About Resilience
Organizations cannot assume that blocking one campaign ends the threat.
They must build systems capable of detecting the next variation.
Grandoreiro’s Story Is Not Over
The latest Mexican campaign is another chapter in a much longer story.
The important question is no longer whether Grandoreiro exists.
The important question is how much more sophisticated its operators can become.
✅ Grandoreiro Has a Long History of Banking Theft
The malware first appeared around 2016 and has been associated with attacks against financial institutions and customers across multiple regions. Its capabilities include credential theft and other forms of surveillance.
✅ Law Enforcement Disrupted the Operation in 2024
Brazilian and Spanish authorities, with international cooperation including Interpol, disrupted parts of the Grandoreiro operation and arrested five alleged administrators. However, disruption did not permanently eliminate the malware family.
✅ The New Campaign Uses DLL Sideloading
The reported Mexican campaign uses a legitimate application as part of a DLL sideloading chain, allowing malicious code to be loaded through trusted software.
✅ The Malware Uses Anti-Analysis Techniques
The loader reportedly examines hardware, software, system activity, and security tools to determine whether it is running in an analysis environment.
❌ A Law-Enforcement Takedown Does Not Mean Grandoreiro Was Completely Destroyed
The evidence does not support the idea that the 2024 operation eliminated Grandoreiro entirely. Current activity demonstrates that parts of the ecosystem survived or were rebuilt.
⚠️ Exact Victim Numbers Remain Limited
The newly reported campaign has produced telemetry showing victims in Mexico and smaller numbers elsewhere, but the available information does not establish a precise global victim count for this particular campaign.
Prediction
(+1) Grandoreiro Will Continue Expanding Its Evasion Capabilities
The latest loader suggests that operators are investing in detection avoidance rather than simply relying on older malware delivery techniques. Future versions are likely to become more modular and more difficult to analyze.
(+1) DLL Sideloading Will Remain Popular
As long as legitimate applications can be manipulated to load malicious libraries, attackers will continue using the technique. Its simplicity and ability to blend malicious activity into trusted processes make it attractive.
(+1) Latin America Will Remain a Major Battlefield
Mexico and other Spanish-speaking markets are likely to remain important targets because Grandoreiro has an established operational history in the region.
(-1) Traditional Signature-Only Detection Will Become Less Reliable
Loaders that dynamically retrieve payloads and inspect their environments can change faster than static signatures can keep up.
(+1) Behavioral Detection Will Become More Important
The combination of suspicious archive extraction, unusual DLL loading, system reconnaissance, and unexpected network communication provides defenders with stronger opportunities to detect future campaigns.
The Bigger Lesson Behind Grandoreiro’s Return
Grandoreiro’s resurgence is a reminder that cybercrime rarely ends with a single takedown.
Criminal infrastructure can be dismantled.
Operators can be arrested.
Servers can disappear.
But the knowledge, financial incentives, stolen code, criminal relationships, and techniques behind an operation can survive.
The Mexican campaign demonstrates exactly why defenders must continue watching threats even after they appear to have declined.
Grandoreiro may not be operating at the scale it once reached, but its latest evolution makes one point painfully clear: a quieter threat is not necessarily a safer threat.
For banks, businesses, and individual customers, the safest approach is to treat suspicious invoices, compressed attachments, unexpected executables, unusual DLL activity, and abnormal outbound connections as potential pieces of a larger attack chain.
The malware may have been born years ago.
Its tactics are still learning.
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