Removal instructions for the Warmcookie backdoor-type malware

What kind of malware is Warmcookie?

Warmcookie is the name of a backdoor-type malware. Malicious programs within this classification are designed to open a "backdoor" to compromised systems; the goal is to cause further infection (i.e., download/install additional malware).

Warmcookie has been around since at least the spring of 2024, with suspected older versions being released even earlier. At the time of writing, this backdoor is actively spread via targeted email spam campaigns.

Warmcookie malware overview

The capabilities of Warmcookie are not extensive, and that is not uncommon for backdoors since their purpose is to serve as an initial entry point to a targeted network. Warmcookie has anti-analysis features, including anti-debugging and detection when launched in sandbox environments. The backdoor can escalate its privileges and ensure persistence by scheduling to run every ten minutes.

Following successful infiltration, in its first stage, Warmcookie collects information for infected machine identification – volume serial number, DNS domain, device name, and username. The gathered data is then sent to the attackers' C&C (Command and Control) server, which is hardcoded into the malware.

In the second stage, Warmcookie aims to extract additional information and begins using the functionalities at its disposal. The program seeks CPU details, victim's IP address, and a list of installed software (including name, version, and installation date).

Warmcookie can execute commands on infected systems. It can read files, take screenshots, and download files onto compromised devices. The latter is the core purpose of Warmcookie, as that is how it causes further infections.

Theoretically, backdoors can infiltrate just about any type of malware into systems; however, in practice, these programs tend to operate within certain limitations. To expand upon the malware that could be installed further down the line – the infection could culminate in some form of a trojan virus.

"Trojan" is an umbrella term encompassing a variety of malicious programs that include (but are not limited to): loaders/downloaders that install additional malware, injectors that inject malicious code into processes/programs, stealers that extract data from systems and apps, spyware that records data (e.g., takes screenshots, streams desktops, records audio/video via microphones/cameras, etc.), grabbers that download files from devices, keyloggers that record keystrokes, clippers that replace clipboard content, and so forth.

Ransomware is another widespread malware. This malicious software encrypts files and/or locks device screens in order to make ransom demands for decryption/ access recovery. It is pertinent to mention that ransomware leveraged against corporate entities often utilizes double extortion tactics, wherein sensitive information is stolen from devices, and victims are forced to comply with the ransom demands under the threat of data leaks.

It is likewise noteworthy that malware developers commonly improve upon their software and methodologies. Therefore, potential future variants could be more streamlined or have additional/different capabilities.

To summarize, the presence of software like Warmcookie on devices can lead to multiple system infections, data loss, severe privacy issues, financial losses, and identity theft.

Backdoor-type malware examples

We have written about thousands of malicious programs; NICECURL, TAMECAT, MadMxShell, XRed, GoBear, and SPICA are just some of our articles on backdoors.

Malware can be highly versatile or have an incredibly narrow purpose. Yet regardless of how a malicious program operates – its presence on a device threatens system and user safety. Therefore, it is paramount to eliminate all threats immediately upon detection.

How did Warmcookie infiltrate my computer?

At the time of research, Warmcookie was proliferated via targeted spam emails. The letters used work and job offer related lures. They impersonated messages from existing recruitment firms and addressed victims using their actual names, as well as indicated their current place of employment, position, and similar information.

Recipients were baited into clicking a link in the email that supposedly led to an internal system wherein they could review the job offer. Doing so resulted in a redirection chain, which led through a compromised site (typically hosted on reputable domains), and landed on a malicious website.

The landing page was presented as a continuation of the initial recruitment lure, and some included information associated with and relevant to the victim. This site prompted the visitor to download the document (detailing the proposed position), and to do so – they were asked to complete a CAPTCHA test.

After it was completed, the victim downloaded an obfuscated JavaScript file. This file ran a PowerShell script intended to infect systems with Warmcookie.

Currently, these campaigns are active and highly maintained. The spam mail is delivered on a daily to weekly basis; likewise, the websites in the redirect chain and the landing pages are updated almost weekly, thus diminishing chances of detection when the reputation of a page rises in notoriety.

It must be mentioned that Warmcookie could be spread by employing different lures, distribution techniques, and infection chains.

Phishing and social engineering are crucial in malware distribution. Malicious programs are typically disguised as or bundled with regular software/media files. Aside from JavaScript, infectious files can arrive as archives (ZIP, RAR, etc.), executables (.exe, .run, etc.), documents (Microsoft Office, Microsoft OneNote, PDF, etc.), and other formats.

The most commonly used malware proliferation methods include: malicious attachments/links in spam (e.g., emails, DMs/PMs, SMSes, social media/ forum posts, etc.), drive-by (stealthy/deceptive) downloads, dubious download sources (e.g., freeware and free file-hosting websites, P2P sharing networks, etc.), online scams, malvertising, pirated programs/media, illegal software activation tools ("cracks"), and fake updates.

Furthermore, some malicious programs can self-spread via local networks and removable storage devices (e.g., external hard drives, USB flash drives, etc.).

How to avoid installation of malware?

We highly recommend exercising caution with incoming emails, DMs/PMs, SMSes, and other messages. Attachments or links in dubious/irrelevant mail must not be opened, as they can be malicious. Another recommendation is to be careful while browsing since fake and dangerous online content usually appears genuine and innocuous.

Additionally, all downloads must be made from official and verified channels. We advise activating and updating programs by using legitimate functions/tools, as those acquired from third-parties may contain malware.

It is essential for device/user safety to have a dependable anti-virus installed and kept updated. Security software must be used to perform regular system scans and to remove detected threats and issues. 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.

Spam email proliferating Warmcookie malware (image source – Elastic):

Text presented in this email:

We're Interested

Your Next Step: A Potential Position

Hello,

We have an exciting opportunity to share with you - a new position available with one of our esteemed clients. Given your outstanding professional background, work experience at SPIRIANT and skills, we believe you could be an ideal fit for this role.

Please access our internal system via the link below to review the detailed job description and associated responsibilities thoroughly.

If the role aligns with your career objecties, we would be thrilled to set up a conversation at your earliest convenience to explore further.

View Position Details

Malicious website (promoted via spam email) proliferating Warmcookie (image source – Elastic):

Update October 3, 2024 – new distribution method discovered in use to spread the Warmcookie backdoor. It has been observed proliferating under the guise of updates for Google Chrome, Microsoft Edge, Mozilla Firefox, and Java (other disguises are possible).

These fakes were hosted on legitimate sites that had been compromised and deceptive pages with domains in line with the malicious content (i.e., update). When victims press the download options on these websites, they trigger JavaScript for retrieving the WarmCookie backdoor installer – which they are prompted to install.

Webpage promoting a fake Edge update that proliferates Warmcookie (image source – BleepingComputer):

Update 30 October, 2024: The latest version of the WarmCookie malware has been updated to make it more effective and harder to detect. One major change is how it maintains a presence on infected computers. It switched from using a command that established persistence to a new one, which could make it more difficult to remove.

The malware also now mimics a standard web browser in its communications, helping it avoid detection by security tools. Additionally, there is a new feature that allows it to update itself. Other changes have improved its ability to avoid detection in security environments.

Overall, WarmCookie is designed to stay on infected systems for a long time and is often used to deliver other harmful software (including CSharp-Streamer-RAT and Cobalt Strike).

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

---

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

---

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

---

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

---

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

---

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

Malware removal rarely necessitates formatting.

What are the biggest issues that Warmcookie malware can cause?

The dangers posed by an infection depend on the malware's capabilities and the cyber criminals' goals. The threats associated with Warmcookie are variable, as this program is a backdoor – malware designed to cause chain infections (i.e., infiltrate additional malicious software). Generally, high-risk infections are linked to data loss, severe privacy issues, financial losses, and identity theft.

What is the purpose of Warmcookie malware?

Malware is predominantly used for profit. However, cyber criminals may also use this software to amuse themselves, realize personal grudges, disrupt processes (e.g., sites, services, companies, etc.), engage in hacktivism, and launch politically/geopolitically motivated attacks.

How did Warmcookie malware infiltrate my computer?

Warmcookie has been observed being actively spread via targeted email spam campaigns. Aside from spam, other widely used malware proliferation methods include drive-by downloads, online scams, malvertising, suspicious download sources (e.g., freeware and third-party sites, P2P sharing networks, etc.), pirated content, illegal software activation tools ("cracks"), and fake updates. Some malicious programs can self-proliferate via local networks and removable storage devices.

Will Combo Cleaner protect me from malware?

Yes, Combo Cleaner is designed to scan computers and eliminate all types of threats. It can detect and remove most of the known malware infections. It must be stressed that running a complete system scan is crucial since sophisticated malicious software tends to hide deep within systems.