How to remove Cutwail malware

What is Cutwail?

Cutwail is malicious software (malware) designed to make infected computers operate as spambots. In this way, infected systems are used to spread spam/send emails. Research shows that cyber criminals use Cutwail to send emails that contain a malicious attachment.

They use these spam campaigns to trick recipients into installing other malware called Dridex and ransomware (e.g. Hermes).

The sent emails are disguised as messages regarding invoices or payment details. Recipients are encouraged to check (open) the attachment, a Microsoft Excel (.xls) file, which is disguised as an invoice form. When this malicious file is opened, MS Excel shows a warning stating that some active content has been disabled, and then opens the file in Protected View mode.

If macros commands are enabled, this malicious .xls file infects the system with Dridex, which is malicious software designed to steal sensitive information such as banking credentials. It does this by recording keystrokes (keys pressed). Stolen banking (and other) accounts could be used to make fraudulent transactions, purchases, etc.

People who have computers infected with this malware are thus likely to experience financial loss. Furthermore, the aforementioned spam campaigns could be used to proliferate other malware, such as Hermes ransomware.

Software of this type encrypts data and keeps it inaccessible until it is decrypted with a decryption tool and/or key, which can only be purchased from the cyber criminals who designed the program (i.e., victims of ransomware are forced to pay ransoms). This software can cause both data and financial loss.

For these reasons, we strongly advise against opening files that are attached to dubious emails (examples are provided below).

Cutwail malware can be used  to spread a variety of malicious programs. Some more examples of high-risk malware that is distributed through spam campaigns are Emotet, Adwind, FormBook, and AZORult. Most cyber criminals distribute this software to generate revenue in various ways.

Typically, victims experience financial loss, problems with privacy, browsing safety, and so on. If your computer is infected with Cutwail or other malware, it should be eliminated as soon as possible.

How did Cutwail infiltrate my computer?

Research shows that cyber criminals proliferate Cutwail via the Pushdo Trojan, which is distributed via spam campaigns (emails). Malicious software is commonly spread through emails - cyber criminals send messages that contain malicious files (attachments) and hope that recipients open them.

Typically, they attach MS Office documents, executable files .exe, JavaScript files, archives such as ZIP, RAR, and so on. If opened, these install malware. In this case, a Trojan is installed. Typically, Trojans proliferate other malicious programs, thereby causing chain infections. In this particular case, once the Trojan is installed, it goes on to install Cutwail.

How to avoid installation of malware

The safest way to download files and programs is using official websites and direct download links. Other sources and tools such as third party downloaders, unofficial websites, Peer-to-Peer networks, etc., should not be trusted. Similarly, irrelevant emails that are received from unknown, suspicious addresses (especially if a file is attached) should not be trusted.

Opening files or web links in these might lead to download and installation of malware. Update all installed software through implemented functions or tools that are designed by official software developers. Unofficial, third party updaters are used to proliferate malware.

The same applies to software activation. Software should not be activated via unofficial ('cracking') tools, since these are illegal and can distribute malicious software. Regularly scan the operating system with a reputable antivirus or anti-spyware suite/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.

Text presented in an email sent through Cutwail:

Subject: Correct payment letter

Dear Partner,
If your payment summary is incorrect, you should request an amended payment summary showing the correct details.

Kind regards,

Everything in this e-mail and the contents of any attachments are confidential, may be legally privileged and are intended solely for the use of the individual to whom it is addressed.  If you are not the intended recipient please delete it and do not disclose, forward or copy this message or its attachments.

Second example of Cutwail spam:

Text presented in this email:

Subject: PLO Logistics Pvt Ltd Invoice for initial payment
Attachment: letter Invoice_form 899 19 Nov 19.xls

Good morning,
 
We certify that we have not yet received the payment regarding the above mentioned proforma invoice.
 
Best Regards,
 
Director

Everything in this e-mail and the contents of any attachments are confidential, may be legally privileged and are intended solely for the use of the individual to whom it is addressed.  If you are not the intended recipient please delete it and do not disclose, forward or copy this message or its attachments.

Third example of Cutwail spam:

Text in this email:

Subject: ZUKD Shipping Correct payment letter
Attachment: Invoice_letter_form_488 20nov19.xls

Dear Partner,
 
Can we make a settlement of the overdue invoices ?
 
Best Regards,
 

Sales department

Everything in this e-mail and the contents of any attachments are confidential, may be legally privileged and are intended solely for the use of the individual to whom it is addressed.  If you are not the intended recipient please delete it and do not disclose, forward or copy this message or its attachments.

Fourth example of Cutwail spam:

Text in this email:

Subject: AAW Global Pte Ltd Invoice for initial payment
Attachment: Invoice_letter_form_065 20nov19.xls

Dear Partner,
 
Please find attached herewith

1 attachments (total)
 
Thanks & Best Regards,
 

JCE Ltd

Everything in this e-mail and the contents of any attachments are confidential, may be legally privileged and are intended solely for the use of the individual to whom it is addressed.  If you are not the intended recipient please delete it and do not disclose, forward or copy this message or its attachments.

Fifth example of Cutwail spam:

Text in this email:

Subject: XEBE LTD Payment
Attachment: letter Invoice_form 049 19 Nov 19.xls

Dear Partner,
 
Please note that the attached prepayment will be sent. Please confirm that that is ok?
 
Thanks & Regards,
 

Chief Financial Officer

Everything in this e-mail and the contents of any attachments are confidential, may be legally privileged and are intended solely for the use of the individual to whom it is addressed.  If you are not the intended recipient please delete it and do not disclose, forward or copy this message or its attachments.

Malicious attachment distributed via Cutwail spam campaigns:

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.