How to remove Lemon Duck malware from the operating system

What is Lemon Duck?

Lemon Duck is malicious software. The primary function of this malware is to exploit the infected machine's resources to mine cryptocurrency, specifically Monero (XMR) cryptocurrency. This malicious program severely compromises infected devices and can even damage them permanently. Lemon Duck was first observed being proliferated in Asia (notably, China), however, its reach has spread exponentially.

Lemon Duck malware overview

Lemon Duck malware infects Windows Operating Systems, however, it specifically targets Windows 7. Since Microsoft has discontinued developing updates for this OS (Operating System) version, it is especially vulnerable to malicious attacks. Cryptocurrency mining on a large scale requires expensive equipment, hence cyber criminals have devised a method of exploiting infected devices to obtain the necessary resources.

The hijacked machines with user level (or close to this level) access are collectively employed to mine cryptocurrency. In simple terms, this currency is mined using computers to solve mathematical problems. This is done by misusing the computer processors (CPUs) and graphics cards (GPUs).

This is essentially the purpose and operation of Lemon Duck. The degree to which cryptominers such as Lemon Duck can misuse the hijacked device is significant. The system can be used to its fullest, taking up to 100% of resources, which can lead to it becoming practically unusable.

It can render the computer unresponsive, or force it to reboot due system overloading. Furthermore, systems running at such capacity tend to generate excessive heat. This can lead to hardware overheating, and more so under certain conditions (e.g. high room temperature, poor cooling systems, etc.).

Therefore, the device itself can be damaged and the data stored within the system might be permanently lost. Typical symptoms of these infections are system lags and/or unresponsiveness, significant increase in temperate generated when normally using the device, etc.

If it is suspected or known that Lemon Duck (or other malware) has ready infiltrated the system, you are strongly advised to use an anti-virus suite to eliminate it immediately.

Cryptominer-type malware examples

BitCoinMiner, COINMINER, and JSMiner-C are some examples of other malicious programs similar to Lemon Duck. Cryptominers can mine various cryptocurrencies and they are not exclusive to Monero. Despite this, the end goal is identical: to generate profit for the cyber criminals behind them. Malware of this type can seriously damage an infected device and, therefore, it is crucial to remove it without delay.

How did Lemon Duck infiltrate my computer?

Malware has various distribution methods. Popular ones include spam campaigns, Trojans, illegal activation tools ("cracks"), fake updaters and untrusted download channels. Spam campaigns are used to send thousands of deceptive/scam emails.

These messages contain infectious files attached to them or download links of malicious content. Lemon Duck has been observed being proliferated using spam campaigns. Infectious files can be in various formats (e.g. Microsoft Office and PDF documents, archive and executable files, JavaScript, etc.).

When they are opened, the infection process starts (i.e., download/installation of malware). Trojans are malicious programs, some of which are capable of causing chain infections. "Cracking" tools can download/install malware rather than activating the licensed product.

Fake updaters infect systems by abusing flaws of outdated products and/or simply by installing malicious software, rather than the promised updates.

Malware is often downloaded unintentionally from dubious sources such as unofficial and free file-hosting (freeware) sites, P2P sharing networks (BitTorrent, eMule, Gnutella, etc.) and other third party downloaders.

How to avoid installation of malware

You are advised against opening suspicious or irrelevant emails, especially those received from unknown/suspect senders (addresses). Any attachments or links present in dubious messages must never be opened, as doing so can lead to high-risk system infection.

Use only official and verified download channels. Activate and update products with tools/functions provided by legitimate developers. Illegal activation ("cracking") tools and third party updaters should not be used, as they are known to be used for malware distribution.

To ensure device integrity and user safety, it is paramount to have a reputable anti-virus/anti-spyware suite installed. This software must be kept updated, used to run regular system scans and to remove all 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.

Malicious attachment distributing Lemon Duck:

Update July 23, 2021 - In the past, LemonDuck malware had been particularly active in China; however, its operations have expanded to include Vietnam, Korea, India, United States, Canada, Russia, United Kingdom, Germany, France, and other countries.

Furthermore, LemonDuck has been redesigned to be a cross-platform malware. In addition to newer Windows versions, it also targets Linux operating systems. While this malicious program was primarily focused on cryptocurrency mining, it can now remove certain security controls, steal log-in credentials (e.g., from email clients), and inject devices with additional malware.

It has been observed infecting compromised systems with RATs (Remote Access Trojans) and Ramnit malware. More information on these developments can be found on the Microsoft Security blog.

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 Lemon Duck malware, should I format my storage device to get rid of it?

No, Lemon Duck's removal does not necessitate formatting.

What are the biggest issues that Lemon Duck malware can cause?

Lemon Duck is a cryptominer - malware designed to abuse system resources to mine (generate) cryptocurrency. Therefore, its infections can lead to diminished system performance or failure, data loss, hardware damage, and financial losses. Furthermore, some versions of Lemon Duck have data-stealing functionalities - which can likewise cause financial loss and lead to severe privacy issues, as well as identity theft.

What is the purpose of Lemon Duck malware?

Most malicious programs are used to generate profit, and Lemon Duck's abilities are designed for the same purpose. However, it is worth mentioning cyber criminals also use malware to amuse themselves, disrupt processes (e.g., websites, services, companies, etc.), realize personal grudges, and even launch politically/geopolitically motivated attacks.

How did Lemon Duck malware infiltrate my computer?

Malicious software is mainly proliferated via drive-by downloads, spam emails and messages, dubious download channels (e.g., freeware and third-party websites, P2P sharing networks, etc.), online scams, illegal program activation tools ("cracks"), and fake updates. Furthermore, some malware can self-spread through local networks and removable storage devices (e.g., external hard drives, USB flash drives, etc.).

Will Combo Cleaner protect me from malware?

Yes, Combo Cleaner is capable of detecting and eliminating most of the known malware infections. It is noteworthy that high-end malicious programs tend to hide deep within systems - hence, running a complete system scan is crucial.