How to eliminate GuLoader (CloudEyE) from the operating system

What kind of malware is GuLoader?

GuLoader (also known as CloudEyE) is a malware downloader used by cyber criminals to proliferate various Remote Access Trojans (RATs) and other Trojan-type programs. They use GuLoader to infect computers with malicious programs that can be used to steal sensitive information, infect computers with other malware, and perform other actions to help cyber criminals generate revenue.

More about the GuLoader malware

Research shows that GuLoader is used to proliferate various RATs and stealers (malicious programs that collect sensitive data).

RAT programs give cyber criminals control over infected computers/operating systems and allow them to log keystrokes, download and execute various files, access webcams, microphones, take screenshots, monitor computing activity, manage (copy, rename, delete) files, and perform other actions.

In most cases, cyber criminals attempt to steal credit card details, credentials (passwords, logins) of accounts, which can be used to make fraudulent purchases, transactions and generate revenue in other ways. RATs are commonly used to infect computers with other malware including ransomware. 

Furthermore, GuLoader is often used to infect computers with malicious programs that steal sensitive information. Cyber criminals behind information stealers usually target banking-related details, passwords, logins, data saved on clipboard, and other sensitive information.

They attempt to infect operating systems with GuLoader to cause chain infections. I.e., infect computers with other malware that can help them to generate revenue. Victims of malware that is proliferated through GuLoader risk suffering monetary and/or data loss, becoming victims of identity theft, experiencing problems relating to online privacy, and other serious issues.

Therefore, if GuLoader or its payload is already installed on the operating system, it should be eliminated immediately.

What other damage GuLoader malware can cause?

Some examples of malicious programs that cyber criminals can spread via GuLoader are Agent Tesla, FormBook, LokiBot, NetWire, Remcos and Vidar. They might also use this downloader to infect systems with other malicious programs.

Their main goal is to gain access to personal information and accounts, or perform other actions that enable them to generate revenue in fraudulent ways.

How did GuLoader infiltrate my computer?

Cyber criminals commonly proliferate malicious programs through spam campaigns, dubious download channels, unofficial (fake) software updating tools, Trojans and software 'cracking' tools/unofficial activators. Spam campaigns are often used to trick recipients into infecting systems through malicious attachments (or web links that download malicious files).

When opened, the files or attachments install malware. Examples of files that cyber criminals include/attach to their emails are Microsoft Office, PDF documents, archive files (e.g., RAR, ZIP), executable files (.exe) and JavaScript files.

Peer-to-Peer networks (torrent clients, eMule), freeware download websites, free file hosting websites, third party downloaders, unofficial pages, etc., are also used to distribute malicious programs. Cyber criminals employ them to host malicious files that, if downloaded and opened/executed, infect operating systems with high-risk malware.

Note that third party installers can also proliferate malware. Unofficial tools that supposedly update installed software can infect operating systems by exploiting bugs/flaws of outdated software, or by installing malicious software rather than updates and fixes. Trojans can cause damage only if they already installed.

These malicious programs can open 'backdoors' for other malware. In this way, they cause chain infections. Software 'cracking' tools are used by people who seek to activate software free of charge (bypass activation), however, they often install malicious software instead.

How to avoid installation of malware

Website links and attachments that are presented in irrelevant emails should not be trusted, especially if the emails are sent from unknown, suspicious addresses. If there is a reason to believe that an email is untrusted, the best option is to simply ignore it and leave its contents unopened.

Software should be downloaded from official websites and via direct download links. Third party downloaders, installers, unofficial pages and other channels/tools should not be used. Installed software must be updated and activated only with tools/functions provided by official developers.

Third party updaters and activators can install malware. Furthermore, it is illegal to bypass activation of licensed software with third party tools. Keep operating systems safe by scanning them for viruses and other threats regularly. These scans should be performed with reputable antivirus or anti-spyware software.

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.

Appearance of a Coronavirus-related spam email used to spread GuLoader malware (attachment is a .gz archive, which contains the executable "QUOTE 2020.PDF.exe"):

Text presented within this email:

Subject: URGENT NEED: U.S. Department of Health & Human Services/COVID-19 Face Mask/ Forehead thermometers

Due to the wild spread of COVID-19 all over the United States, the U.S. Department of Health & Human Services is in urgent demand of Face mask and forehead thermometers for it's citizens.

I will like if your company can supply us with the attached products list.

Awaiting your urgent reply.

Best regards.

Sheila Conley

U.S. Department of Health & Human Services
200 Independence Avenue, S.W.

Other examples of spam emails used to spread GuLoader malware:

Sample 1:

Screenshot of a malicious MS Excel document ("complete_3.xlsm") attached to this spam email:

Sample 2:

Sample 3:

Text presented within:

Subject: DHL Air Waybill Number: 290132721

Hello,

We thank you for your cooperation and inform you that your cargo has arrived at the warehouse of the DHL Express transport network.

Please sign the attached customs declaration of the attached cargo documents and return it to our agent.

Description:

Air waybill number 290132721 (Physical weight: 1.05 kg; Seats: 1).
 
Greetings
 
Daniele Federici
DHL Global Forwarding
Department Customer Support

Sample 4:

Text presented within:

Subject: LEGAL WARNING AGAINST YOUR COMPANY

 

Good day,

We are Zhang, Mingee & Associates Law Firm, specializing in customs and international trade law. We represent our client, whose pertinent details and invoices are attached, in the matter of the settlement of long-overdue invoices that remain unpaid despite numerous reminders.

This letter serves as a formal notification that if the outstanding invoice is not settled by March 30th, 2025, we will commence legal proceedings against your company to recover the debt.

Please find enclosed the legal notice, which has also been dispatched to your office via courier for your reference.

Sincerely,

JIM MINGEE
808 Green Springs Hwy Homewood,

AL 35209 ; 5355 Executive Place, Jackson, MS 39206

(601) 940-2577

(214) 296-3186

Sample 5 (source: asec.ahnlab.com):

Examples of Die Post-themed spam emails distributing GuLoader malware (the attachment is a link leading to a malicious executable):

Update November 11, 2024: A new GuLoader campaign has recently emerged, targeting European industrial and engineering firms with spearphishing emails. The campaign focuses on companies in countries like Romania, Poland, Germany, and Kazakhstan, often sending emails that appear as order inquiries.

These emails contain archive file attachments (e.g., ISO, 7z) which, when opened, deploy GuLoader malware. The attackers use compromised or fake email addresses and often hijack existing email accounts to appear more legitimate, increasing the chances of recipients downloading malware.

Businesses in the affected sectors are advised to exercise caution when handling unexpected attachments.

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.

Frequently Asked Questions (FAQ)

My computer is infected with GuLoader malware, should I format my storage device to get rid of it?

GuLoader can be removed from the storage device without having to format it. Our malware removal guide is provided above.

What are the biggest issues that malware can cause?

It can encrypt files, slow down a computer, inject other malware, steal sensitive information, mine cryptocurrency, and more. It depends on the type of malware.

What is the purpose of GuLoader malware?

GuLoader is used to distribute other malware (mainly remote access Trojans). The malware injected via GuLoader can be used to remotely control/access computers, encrypt files, steal identities, personal accounts, money, etc.

How did a malware infiltrate my computer?

It is known that GuLoader is delivered via email. Cybercriminals send emails containing malicious attachments (or links) to trick recipients into downloading this malware. Also, malware is distributed using malicious drive-by downloads, cracked software download pages, and other untrustworthy sources for downloading software (or files).

Will Combo Cleaner protect me from malware?

Yes, Combo Cleaner will detect and remove malware. It can detect almost all known malware. It is important to mention that high-end malware can hide deep in the operating system. Thus, it is required to run a full scan to remove malware of this kind.