How to uninstall the Guildma Trojan from the operating system

What is Guildma Trojan?

Guildma is malicious software exclusively targeting Brazil and classified as a banking Trojan. While some variants of this malware have been updated to widen its range to other territories, no observations have been made of such attacks being carried out.

Furthermore, later versions had these capacities removed entirely. Guildma is the most sophisticated banking Trojan in the region of Brazil. In comparison with similar malicious programs targeting this country, Guildma uses the most advanced execution (i.e., infection) techniques.

With its various capabilities/features, this Trojan can cause especially serious issue and is, therefore, high-risk.

Guildma targets financial institutions of Brazil, however, its scope of potential targets is larger. It also attempts to exfiltrate (i.e., steal) data relating to emails, e-commerce (i.e., online stores) and streaming service accounts.

Unlike most banking Trojans operating in Brazil, Guildma has greater capacity to communicate with its C&C (Command and Control) server, which allows it more versatility in carrying out its malicious operations. Following successful infiltration, this malware checks whether it is running on a virtual machine or a "sandboxed" environment.

It also inspects the system's geolocation and other details. If the information is of no interest, Guildma terminates itself. If this data matches relevant criteria, the Trojan begins collecting system information (e.g. device name, installed software, etc.) and connects to the C&C server.

Guildma then begins monitoring pertinent activity such as when a banking website is opened. The malware can take screenshots and has keylogging capabilities as well. Therefore, it can record key strokes, which can be used to steal log-ins and passwords of various accounts.

Typically, Guildma monitors when a relevant web page is opened through Internet Explorer and forcefully logs the user out. It then gathers the log-in information when an attempt to access the account is made. Another particular area of interest for this Trojan are emails.

It can extort data from popular email clients and browsers. The malware collects email addresses and forms from sites. It can even collect email addresses and contact lists from desktop email clients (e.g. Microsoft Outlook, Thunderbird, The Bat!, etc.).

Other capabilities/features of the malicious program include emulating keyboard and mouse inputs, blocking shortcut keys (e.g. Alt + F4, which is used to closed the current activate window - by blocking this command, Guildma can prevent users from closing pop-ups that it displays, and so on).

It can also execute and exfiltrate (i.e., download) files, reboot the system, etc. In summary, Guildma can cause significant financial loss, serious privacy issues and lead to identity theft. If it is known or suspected that the Guildma banking Trojan (or other malware) has already infected the system, you are strongly advised to use anti-virus software to remove it immediately.

Cinobi, Grandoreiro, Lampion, Mispadu and Bolik are some examples of other banking Trojans. Their functionalities differ, however, the purpose is identical: to generate revenue for the cyber criminals behind them. This malware endangers system integrity, affects its operation and can even cause data/system damage.

If such infections are not eliminated promptly, they can threaten user safety. Therefore, immediate removal is crucial.

How did Guildma infiltrate my computer?

Guildma has been observed being proliferated through spam campaigns. The term "spam campaign" defines a large scale operation, during which deceptive/scam emails are sent by the thousand.

The content of the messages used to distribute Guildma is varied, ranging from short messages intended to rouse user curiosity (e.g. requests for explanation of unspecified photographs) to fake invoices reminding users of approaching payment deadlines. Infections are caused via infectious files attached to (or linked inside) such emails.

Malicious files can be in various formats (e.g. archive and executable files, PDF and Microsoft Office documents, JavaScript, etc.). Once an infectious files is opened, the infection process is initiated (i.e., malware download/installation begins).

Other popular proliferation methods of malicious content include backdoor Trojans, illegal activation tools ("cracks"), bogus updates and untrusted download sources. Some Trojans can cause chain infections. "Cracking" tools can download/install malicious software rather than activating licensed products.

Fake updaters infect systems by exploiting weaknesses of outdated products and/or simply by installing malware rather than the promised updates.

Untrustworthy download channels (e.g. unofficial and free file-hosting websites, Peer-to-Peer sharing networks and other third party downloaders) can offer malicious programs for downloading, disguised as or bundled with normal products.

How to avoid installation of malware

Dubious and/or irrelevant emails should not be opened, especially those received from unknown/suspect senders. You are strongly advised against opening files or links present in suspicious mail, as this can lead to high-risk infection. Use only official and verified download sources.

It is also important to activate and update products with tools/functions provided by genuine developers. Illegal activation ("cracking") tools and third party updaters should not be used, as they are often employed to distribute malware. To ensure device and user safety, it is paramount to have a reputable anti-virus/anti-spyware suite installed.

It must be kept up to date, used to run regular system scans and to remove detected/potential threats. If you believe that your computer is already infected, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.

Screenshots of malicious spam emails used to spread Guildma trojan (each contains a link leading to a malicious archive file containing Guildma malware executable);

Example 1:

Text presented within:

Subject: Nf-Stock - Novo documento disponivel 04 - [Cliente Credenciado - ********]

(NF-Stock) #ULK6HMRCL3N063685G9KB0N8JI6UV
NF stock
alterdata
Bom dia, ********
Você recebeu 1 nova nota no NFStock.
N:8375656556488240
Para visualizá-las, Notas-NFStock [N:40/83756]

Example 2:

Text presented within:

Subject: Documento Liberado

 

PRESERVE A NATUREZA, EVITE O DESPERDÍCIO DE PAPEL E PENSE ANTES DE IMPRIMIR.

"Responsabilidade com o MEIO AMBIENTE"
Abrir Imprimir Doc. 7854858

Esta mensagem e quaisquer arquivos em anexo podem conter informações confidenciais e/ou privilegiadas. Se você não for o destinatário ou a pessoa autorizada a receber esta mensagem, por favor não leia, copie, repasse, imprima, guarde, nem tome qualquer ação baseada nestas informações. Por favor notifique o remetente imediatamente por e-mail e apague a mensagem permanentemente. Este ambiente está sendo monitorado para evitar o uso indevido de nossos sistemas.

Example 3:

Text presented within:

Subject: Envio da NFe - N.Doc: 346624 - Série: 52

 
Seguem dados da NF-e em anexo.

Caso não consiga visualizar o email acesse este link

Autorizado o uso da NF-e
Chave de acesso: 84322601566588244420971526723526015
Dados da NF-e
Número: 1526723526015     Série: 2     Data de Emissão: 01/02/2021
Protocolo de Autorização: 665882444209726015 12/04/2021 06:50:20
Ambiente: Produção     Tipo de Emissão: Normal
Valor da NF-e: R$ 2.484,03

Importante

As informações contidas nesta mensagem são CONFIDENCIAIS e protegidas pelo sigilo legal. A divulgação, distribuição ou reprodução do teor deste documento depende de autorização do emissor. Caso V. Sa. não seja o destinatário, preposto ou a pessoa responsável pela entrega desta mensagem, fica, desde já, notificado que qualquer divulgação, distribuição ou reprodução é estritamente proibida, sujeitando-se o infrator às sanções legais Caso esta comunicação tenha sido recebida por engano, favor nos avisar imediatamente, através do email: (pedidos@centermassas.com.br)
 
Baixar (Nota Fiscal Eletrônica)

Mensagem gerada automaticamente. Não responder.

How to remove malware manually?

Most trojan infections can be removed by running a full system scan with Combo Cleaner. The full manual procedure below is for cases where automatic removal failed, where you want to verify a scan caught everything, or where the threat has multiple persistence points.

Tools you'll need

Combo Cleaner Antivirus 7-days free trial

Recommended primary scanner. VB100 certified. The 7-day free trial is available.

Microsoft Defender Offline Free · built-in

Built into Windows. Boots to a clean environment to catch rootkits.

Process Explorer Free

From Microsoft Sysinternals. Better than Task Manager - shows full paths and signatures.

Autoruns Free

From Microsoft Sysinternals. Lists every place malware can persist on your system.

Microsoft Safety Scanner (MSERT) Free

Official Microsoft on-demand scanner. Always-current signatures - expires every 10 days.

Phase 1~ 5 min

Contain - limit the damage

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1

Disconnect from the network

30 secNo tool needed

Unplug your Ethernet cable and turn off Wi-Fi. If you're on a laptop, the airplane-mode key works fastest.

Why this matters

Many trojans exfiltrate data - saved browser passwords, banking sessions, screenshots - and accept remote commands. Cutting the network stops both immediately. Keep it disconnected until Phase 4.

2

Boot into Safe Mode with Networking

3 min

Safe Mode loads a minimal set of drivers and stops most malware from auto-running. "With Networking" lets you download tools - re-enable Wi-Fi only after you've booted in.

Windows 11

Open Settings → System → Recovery. Click Restart now next to Advanced startup.

Your computer will restart into the "Choose an option" menu. Click Troubleshoot → Advanced options → Startup Settings → Restart. After the second reboot, press 5 or F5.

Windows 10

Click the Windows logo, hold Shift, click the Power icon and choose Restart. In the Choose an option screen, click Troubleshoot → Advanced options → Startup Settings → Restart. Press F5.

Windows 8

Go to the Start Screen, type Advanced, select Settings → Advanced startup options → Restart now → Troubleshoot → Advanced options → Startup settings → Restart → F5.

Note: Windows 8 reached end-of-life in January 2023 - running on it puts you at much higher risk of reinfection.

Windows 7

Click Start → Shut Down → Restart → OK. As the system boots, press F8 repeatedly until the Windows Advanced Options menu appears, then choose Safe Mode with Networking.

Note: Windows 7 reached end-of-life in January 2020 - running on it puts you at much higher risk of reinfection.

Phase 2~ 15 min

Identify - find what's hiding

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3

Inspect running processes with Process Explorer

Tool: Process Explorer5 min

Download Process Explorer from Microsoft Sysinternals. Run it as Administrator. Click Options → Verify Image Signatures and View → Lower Pane View → DLLs.

Sort by "Verified Signer." Anything unsigned running from %AppData%, %LocalAppData%, %Temp%, or %ProgramData% is suspicious. Right-click → Properties to see the full image path. Right-click → "Search Online" to look up unfamiliar process names.

Why not just Task Manager

Task Manager hides full file paths, doesn't show digital signatures, and groups processes in ways that make malware easy to miss. Process Explorer is the same tool Microsoft engineers use.

4

Map every persistence point with Autoruns

Tool: Autoruns 14.x10 min

Download Autoruns. Right-click Autoruns.exe and choose Run as administrator - without elevation, Autoruns can't inspect protected registry hives.

In the menu, open Options → Hide Microsoft Entries and Options → Hide Empty Locations, then click Refresh.

Modern trojans don't just live in startup. Walk through these tabs and look for unsigned or unfamiliar entries:

• Logon - classic Run/RunOnce keys
• Scheduled Tasks - frequent hiding spot, especially tasks with PowerShell, MSHTA, or rundll32 actions
• Services - unsigned services in non-Microsoft folders
• WMI - Event Subscriptions are a stealthy persistence mechanism (MITRE T1546.003)
• Image Hijacks - Image File Execution Options "Debugger" abuse
• AppInit - DLLs loaded into every GUI process
• Browser plug-ins - unsigned add-ons across all installed browsers

Pro tip

Right-click any suspicious entry → "Jump to Image" to see the actual file. Right-click → "Search Online" opens VirusTotal for the file hash. Don't delete yet - just write down the file paths and entry names. We'll remove them after the scans.

5

Check the hosts file and DNS settings

3 minBuilt into Windows

Trojans often redirect bank, antivirus, and update domains to attacker-controlled servers by editing the hosts file or DNS settings.

Hosts file: Open Notepad as Administrator and open C:\Windows\System32\drivers\etc\hosts. Legitimate entries are commented with #. Any uncommented IP-to-domain mapping is suspicious - especially redirects for microsoft.com, windowsupdate, or your bank.

DNS settings: Open Command Prompt as Administrator and run ipconfig /all. Confirm your DNS servers point to your ISP, your router, or a known public resolver (Cloudflare 1.1.1.1, Google 8.8.8.8). Then open Settings → Network & internet → [your adapter] → DNS server assignment and verify both DNS and DNS over HTTPS (DoH) settings haven't been hijacked.

Why this matters

A clean PC with hijacked DNS is still a compromised PC. You'll think you're at chase.com and you'll be at the attacker's clone.

Phase 3~ 60-90 min

Remove - three scans, one cleanup

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No single antivirus catches everything. The order below is intentional: offline scan first (catches rootkits before Windows fully loads), then on-demand scanners on the running system, then manual cleanup of anything they missed.

6

Run Microsoft Defender Offline

Tool: Built into Windows15 min

Reboot to normal Windows. Open Windows Security → Virus & threat protection → Scan options. Select Microsoft Defender Antivirus (offline scan) and click Scan now. Your computer will restart into a stripped-down environment and scan before the full operating system loads.

Why this comes first

Rootkits and bootkits hide from any scanner running on the same Windows session that's already infected. A pre-boot offline scan sees the disk before the malware can hide itself.

Recommended antivirus

Combo Cleaner

VB100 certified. Includes anti-trojan, registry/persistence scanning, anti-spyware in one pass. The 7-day free trial is available.

Download Combo Cleaner

7

Run Combo Cleaner full system scan

Tool: Combo Cleaner20-40 min

Install Combo Cleaner and run a full system scan (not the quick scan). Let it complete fully, review the detected threats, and apply the recommended actions. Combo Cleaner will quarantine known trojans and registry persistence.

8

Run Microsoft Safety Scanner as a second-opinion scan

Tool: Microsoft Safety Scanner15 min

Download Microsoft Safety Scanner (MSERT.exe), Microsoft's free on-demand tool. The binary expires every 10 days, which means every download has the latest signatures. Run a full scan after Combo Cleaner to catch anything one engine alone might miss.

Why a second scan

Different scanning engines catch different threats. Running an additional Microsoft scan after Combo Cleaner is the single most underused verification step in malware removal.

9

Manually remove anything still listed in Autoruns

Tool: Autoruns10 min

Reopen Autoruns. Anything you flagged in Step 4 that's still present hasn't been caught by the automated scans. For each remaining suspicious entry: right-click → Delete in Autoruns (this removes the persistence registration), then navigate to the file path and delete the actual file. Empty the Recycle Bin.

Important

Some malware files reappear after deletion because something else on the system recreates them. If you delete a file and it returns within minutes, you have a remaining persistence point that Autoruns didn't show - usually a service or scheduled task running under SYSTEM. Re-run the scans from Steps 6-8 or proceed to a clean install (see end of guide).

Phase 4~ 15 min

Recover - restore browsers and security

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10

Reset browsers and clear notification permissions

5 min

Trojans and adware frequently hijack browsers - change the default search engine, install rogue extensions, or grant themselves notification permissions to keep displaying scam pop-ups even after the malware is gone.

• Chrome: visit chrome://settings/reset and click "Restore settings to their original defaults." Then visit chrome://settings/content/notifications and remove any unfamiliar sites.
• Edge: visit edge://settings/reset. Then check edge://settings/content/notifications.
• Firefox: open about:support and click Refresh Firefox (Firefox uses "Refresh," not "Reset"). Then check Settings → Privacy & Security → Permissions → Notifications.

Review installed extensions in each browser and remove anything you don't recognize, especially extensions you didn't install yourself.

11

Re-enable Defender, Tamper Protection, and update everything

10 min

Many trojans disable security software. Open Windows Security → Virus & threat protection → Manage settings and confirm Real-time protection, Cloud-delivered protection, and Tamper Protection are all turned on. Tamper Protection prevents malware from disabling Defender silently.

Then run Windows Update (Settings → Windows Update → Check for updates) and update your browsers and applications. The infection vector that let the trojan in originally usually involves outdated software.

Phase 5~ 15 min + 7 days

Verify & secure

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12

Change passwords from a clean device

20 min⚠ Critical

If the trojan was an info-stealer (Lumma, RedLine, Vidar, and similar are extremely common), assume every password saved in your browser is compromised. Change them from a different, known-clean device - your phone is fine if it's not infected.

Recommended order:

1. Primary email first - it's the recovery hub for everything else
2. Banking and financial accounts
3. Password manager master password (if you use one)
4. Social media, shopping, and remaining accounts

Where available, enable phishing-resistant multi-factor authentication (passkeys / FIDO2 hardware keys / authenticator apps) - SMS-based MFA is bypassable by sophisticated attackers.

13

Verify the clean and monitor for 7 days

5 min + 1 week monitoring

Reconnect to the network and run one final full scan with Combo Cleaner. Open Task Manager (Ctrl + Shift + Esc) and switch to the Startup apps tab - confirm nothing suspicious has reappeared.

Over the next 7 days, watch for symptom recurrence: unexpected high CPU usage, unknown processes returning, browser redirects, or pop-ups. If anything returns, you missed a persistence point and the procedure needs to be repeated - or you may have a deeper compromise that requires a clean install.

When to clean install Windows instead

Manual removal isn't always the right answer. Reinstalling Windows from scratch is the only way to be 100% certain when:

• The malware reappears after every removal attempt
• A bootkit or UEFI rootkit was detected (this class of threat sits below the operating system and survives a normal Windows reinstall)
• A confirmed credential-theft trojan ran with administrator privileges (Lumma, RedLine, Vidar) - the system likely has multiple unknown payloads
• The PC is used for online banking, business email, or anything where partial doubt isn't acceptable

A clean install is a 30-60 minute process: Windows 11 reinstall via Settings → System → Recovery → Reset this PC → Remove everything → Cloud download. Back up documents to external storage first, scan the backup with Combo Cleaner before restoring it, and reinstall applications fresh - never restore them from a backup of the infected system.

Important: Manual removal requires advanced computer skills. If you're not confident identifying system files from malicious files, run an automated scan with Combo Cleaner and Windows Defender and stop there - that path catches the vast majority of consumer trojans without the risk of breaking Windows by deleting the wrong file.