Technology
Microsoft takes down malware found on 394,000 Windows PCs
Infostealer malware has been on the rise recently, and that’s evident from the billions of user records leaked online in the past year alone. This type of malware targets everything from your name, phone number and address to financial details and cryptocurrency. Leading the charge is the Lumma infostealer.
I have been reporting on this malware since last year, and security researchers have called it one of the most dangerous infostealers, infecting millions. There have been countless incidents of Lumma targeting people’s personal data (more on this later), but the good news is that Microsoft has taken it down.
The Redmond-based company announced it has dismantled the Lumma Stealer malware operation with the help of law enforcement agencies around the world.
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Illustration of a hacker at work (Kurt “CyberGuy” Knutsson)
What you need to know
Microsoft confirmed that it has successfully taken down the Lumma Stealer malware network in collaboration with law enforcement agencies around the world. In a blog post, the company revealed that its Digital Crimes Unit had tracked infections on more than 394,000 Windows devices globally between March 16 and May 16.
Lumma was a go-to tool for cybercriminals, often used to siphon sensitive information like login credentials, credit card numbers, bank account details and cryptocurrency wallet data. The malware’s reach and impact made it a favored choice among threat actors for financial theft and data breaches.
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To disrupt the malware’s operation, Microsoft obtained a court order from the U.S. District Court for the Northern District of Georgia, which allowed the company to take down key domains that supported Lumma’s infrastructure. This was followed by the U.S. Department of Justice stepping in to seize control of Lumma’s core command system and shut down marketplaces where the malware was being sold.
International cooperation played a major role as well. Japan’s cybercrime unit helped dismantle Lumma’s locally hosted infrastructure, while Europol assisted in actions against hundreds of domains used in the operation. In total, over 1,300 domains were seized or redirected to Microsoft-managed sinkholes to prevent further damage.
Microsoft says this takedown effort also included support from industry partners such as Cloudflare, Bitsight and Lumen, which helped dismantle the broader ecosystem that enabled Lumma to thrive.
HP laptop (Kurt “CyberGuy” Knutsson)
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More about the Lumma infostealer
Lumma is a Malware-as-a-Service (MaaS) that has been marketed and sold through underground forums since at least 2022. Over the years, its developers have released multiple versions to continually improve its capabilities. I first reported on Lumma in February 2024, when it was used by hackers to access Google accounts using expired cookies that contained login information.
Lumma continued targeting users, with reports in October 2024 revealing it was impersonating fake human verification pages to trick Windows users into sharing sensitive information. The malware wasn’t limited to Windows. In January 2024, security researchers found the infostealer malware was targeting 100 million Mac users, stealing browser credentials, cryptocurrency wallets and other personal data.
Windows laptop (Kurt “CyberGuy” Knutsson)
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6 ways you can protect yourself from infostealer malware
To protect yourself from the evolving threat of infostealer malware, which continues to target users through sophisticated social engineering tactics, consider taking these six essential security measures:
1. Be skeptical of CAPTCHA prompts: Legitimate CAPTCHA tests never require you to press Windows + R, copy commands or paste anything into PowerShell. If a website instructs you to do this, it’s likely a scam. Close the page immediately and avoid interacting with it.
2. Don’t click links from unverified emails and use strong antivirus software: Many infostealer attacks start with phishing emails that impersonate trusted services. Always verify the sender before clicking on links. If an email seems urgent or unexpected, go directly to the company’s official website instead of clicking any links inside the email.
The best way to safeguard yourself from malicious links that install malware, potentially accessing your private information, is to have strong antivirus software installed on all your devices. This protection can also alert you to phishing emails and ransomware scams, keeping your personal information and digital assets safe. Get my picks for the best 2025 antivirus protection winners for your Windows, Mac, Android and iOS devices.
3. Enable two-factor authentication: Enable two-factor authentication (2FA) whenever possible. This adds an extra layer of security by requiring a second form of verification, such as a code sent to your phone, in addition to your password.
4. Keep devices updated: Regularly updating your operating system, browser and security software ensures you have the latest patches against known vulnerabilities. Cybercriminals exploit outdated systems, so enabling automatic updates is a simple but effective way to stay protected.
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5. Monitor your accounts for suspicious activity and change your passwords: If you’ve interacted with a suspicious website, phishing email or fake login page, check your online accounts for any unusual activity. Look for unexpected login attempts, unauthorized password resets or financial transactions that you don’t recognize. If anything seems off, change your passwords immediately and report the activity to the relevant service provider. Also, consider using a password manager to generate and store complex passwords. Get more details about my best expert-reviewed Password Managers of 2025 here.
6. Invest in a personal data removal service: Consider using a service that monitors your personal information and alerts you to potential breaches or unauthorized use of your data. These services can provide early warning signs of identity theft or other malicious activities resulting from infostealer malware or similar attacks. While no service promises to remove all your data from the internet, having a removal service is great if you want to constantly monitor and automate the process of removing your information from hundreds of sites continuously over a longer period of time. Check out my top picks for data removal services here.
Get a free scan to find out if your personal information is already out on the web.
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Kurt’s key takeaway
Microsoft’s takedown of the Lumma Stealer malware network is a major win in the fight against infostealers, which have fueled a surge in data breaches over the past year. Lumma had become a go-to tool for cybercriminals, targeting everything from browser credentials to crypto wallets across Windows and Mac systems. I’ve been tracking this malware since early 2024, and its ability to impersonate human verification pages and abuse expired cookies made it especially dangerous.
Do you feel tech companies are doing enough to protect users from malware like this? Let us know by writing us at Cyberguy.com/Contact
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If you’ve ever clicked “Check for updates” and trusted what you saw, you’re not alone. That’s exactly what this latest scam is counting on.
The page mimics official branding, includes a believable knowledge base number and presents a big blue download button that feels familiar.
The catch? The download installs malware designed to steal passwords, payment details and account access.
According to researchers at Malwarebytes Labs, a cybersecurity research and threat intelligence team inside Malwarebytes, the site uses a typosquatted domain that looks close enough to a real Microsoft URL to fool a quick glance. That small trick is often all it takes.
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Cybersecurity researchers warn a fake Microsoft update site uses a look-alike URL and a familiar download button to deliver data-stealing malware. (Michael Nagle/Bloomberg via Getty Images)
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Why this fake Windows update malware slips past detection
At first glance, nothing seems off. The file looks like a standard Windows installer. It even lists “Microsoft” in its properties. That’s where this attack gets clever. Instead of using obvious malicious code, the attackers built the installer with legitimate tools and layered the attack in stages. Each piece looks harmless on its own.
Here’s what’s happening behind the scenes:
- The installer launches what appears to be a normal app
- That app quietly runs hidden scripts
- A disguised process loads a full Python environment
- Data theft tools activate in the background
Because each step looks routine, many security tools fail to flag it right away. Researchers also noted that antivirus engines initially showed zero detections for key parts of the attack. That does not mean the file is safe. It means the malicious behavior is well hidden.
What this fake Windows update malware is stealing
Once installed, the malware gets to work fast. It collects details about the infected device, including location and IP address. Then it reaches out to remote servers to receive instructions and upload stolen data.
The targets include:
- Saved browser passwords
- Login sessions and cookies
- Payment details
- Discord account tokens
It even tries to shut down other processes on your system to avoid interference while it works. In some cases, it modifies apps like Discord to intercept account activity in real time.
How the fake Windows update malware stays on your system
This malware is designed to stick around. It creates entries that look like normal system processes, so they blend in. One registry entry mimics Windows Security Health, which most users would ignore. It also drops a shortcut in your startup folder with a familiar name like Spotify. That makes it easy to overlook. Two different persistence tricks mean it can survive a reboot and keep running.
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A fake Windows update page is tricking users into downloading malware that steals passwords, payment details and account access. (Beata Zawrzel/NurPhoto)
Why this fake Windows update scam feels so real
There’s a bigger trend behind this. Researchers say campaigns like this often target regions where large data breaches have already exposed personal information. When attackers already know your name, provider or habits, they can build scams that feel tailored to you. That makes a fake Windows update page far more believable than a generic phishing email.
It also highlights something important. Today’s malware often hides inside legitimate tools and trusted frameworks. That makes it harder to detect and easier to trust. This campaign shows how far scammers have come. They are no longer relying on sloppy emails or obvious fake links. Instead, they are building layered attacks that look and behave like trusted software.
Even experienced users can get caught off guard when everything appears normal. The biggest takeaway is simple. A clean scan result or a familiar interface does not guarantee safety.
Microsoft says it’s aware of the threat
Microsoft confirmed it is tracking this type of activity and urges users to be cautious when downloading updates from unfamiliar sources.
“We are aware of reports of fraudulent websites impersonating Microsoft, and we actively work to detect and disrupt malicious activity across the internet,” A Microsoft spokesperson told CyberGuy. “We encourage customers to be cautious of unexpected prompts or downloads and to verify that they are interacting with legitimate Microsoft domains. As a best practice, we recommend users verify the legitimacy of a link by going directly to our website from your own saved favorite, from a web search, or by typing the domain name yourself.”
For more guidance on how to protect against online phishing scams, you can refer to Microsoft’s official support page at support.microsoft.com.
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A convincing Windows update scam is spreading malware that can grab saved passwords, cookies, payment data and Discord tokens. (Todor Tsvetkov/Getty Images)
Ways to stay safe from fake Windows update malware
You don’t need to be a security expert to avoid this. A few habits make a big difference.
1) Only update Windows from your settings
Go to Settings > Windows Update and check for updates there. Avoid downloading updates from websites.
2) Double-check the URL
Real Microsoft pages use microsoft.com. Anything else, even if it looks close, should raise a red flag.
3) Be cautious with urgent update prompts
If a site or message pressures you to install an update, stop and verify it manually.
4) Use strong antivirus software with behavior detection
Traditional antivirus software, which often comes built into your device or as basic security software, mainly looks for known threats using signature matching, which means it can miss new or well-hidden attacks like this one. Strong antivirus software uses behavior detection to monitor what programs are doing in real time, helping flag suspicious activity even if the malware hasn’t been seen before. Get my picks for the best 2026 antivirus protection winners for your Windows, Mac, Android & iOS devices at Cyberguy.com.
5) Use a data removal service to limit your exposure
If your personal information is already circulating online from past breaches, it can make scams like this more convincing. A data removal service helps reduce how much of your information is publicly available, making it harder for attackers to target you with tailored phishing attempts. Check out my top picks for data removal services and get a free scan to find out if your personal information is already out on the web by visiting Cyberguy.com
6) Turn on two-factor authentication
Two-factor authentication (2FA) adds a second layer of protection if your passwords are stolen.
7) Avoid downloading installer files from unknown sites
Legitimate updates rarely require manual downloads.
Kurt’s key takeaways
Fake updates are one of the most effective tricks because they tap into something we all trust. Keeping your system secure should not put you at risk, yet that’s exactly what attackers are exploiting here. The safest move is to slow down, verify where updates come from and stick to built-in tools whenever possible.
Are tech companies doing enough to keep fake updates from putting your data at risk? Let us know your thoughts in the comments below. Let us know by writing to us at Cyberguy.com.
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