Technology
Windows PCs at risk as new tool disarms built-in security
All modern Windows PCs come with Microsoft Defender built in. For the unaware, this tool is Windows’ native antivirus.
Over time, it has matured into a reliable security tool capable of blocking a wide range of threats. However, a tool called Defendnot can shut down Microsoft Defender completely, without exploiting a bug or using malware. It simply convinces Windows that another antivirus is already running.
The implications are serious. This tool does not break into the system or use advanced code injection. It uses Windows features the way they were designed to be used. And that makes the problem harder to detect and harder to fix.
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Windows software on a PC (Kurt “CyberGuy” Knutsson)
The tool works by pretending to be an antivirus
Windows is built to avoid running multiple antivirus products at once. When a third-party antivirus registers itself, Windows disables Microsoft Defender to prevent conflicts. Defendnot exploits this system using an undocumented API that security software uses to communicate with the Windows Security Center.
The tool registers a fake antivirus that appears legitimate to the system. It uses a dummy DLL and injects it into Task Manager, a trusted Windows process. By operating inside this signed process, Defendnot avoids signature checks and permission blocks. Once the fake antivirus is registered, Windows disables Microsoft Defender without warning or confirmation.
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No security alert is shown to the user. No visible changes are made to indicate that the system is unprotected. Unless someone checks manually, the machine remains open to attacks with no real-time protection running.
The tool also includes options to set a custom antivirus name, enable logging and configure automatic startup. It achieves persistence by creating a scheduled task that runs whenever the user logs in.
Windows software on a laptop (Kurt “CyberGuy” Knutsson)
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From GitHub takedown to a fresh build
Defendnot is based on an earlier project called No-Defender. That project used code from an actual antivirus product to fake registration. It gained attention quickly and was removed after a copyright complaint from the vendor whose code had been reused. The developer took the project down and walked away from it.
With Defendnot, the creator rebuilt the core features using original code. This version avoids copyright issues and uses a new method to achieve the same effect. It does not rely on another antivirus or third-party binaries. It was written from scratch to demonstrate how simple it is to manipulate Windows security from inside the system.
Microsoft Defender currently flags the tool as a threat. It detects and quarantines it under the name Win32/Sabsik.FL.!ml. However, the fact that it works at all points to a weakness in how Windows handles antivirus registration and trust.
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Windows laptop showing the home screen (Kurt “CyberGuy” Knutsson)
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6 ways to protect yourself from malicious programs
While Defendnot is a research project, there’s a chance that similar tools are already out there and could be used to compromise your PC. Here are a few tips to help you stay safe:
1. Use strong antivirus software: Even with regular updates, Windows systems can be left exposed by tools like Defendnot that silently disable built-in defenses. A strong third-party antivirus with real-time protection and frequent updates provides essential backup security. Look for solutions with real-time protection and frequent updates to tackle emerging threats. Get my picks for the best 2025 antivirus protection winners for your Windows, Mac, Android and iOS devices.
2. Limit exposure: Many exploits rely on user interaction, such as clicking a shady link, downloading a compromised file or mounting an untrusted virtual disk. Stick to reputable websites, avoid opening unsolicited email attachments and use a browser with built-in security features (like Microsoft Edge or Chrome with Safe Browsing enabled).
3. Avoid running unexpected commands: Never paste or run commands (like PowerShell scripts) you don’t understand or that were copied from random websites. Attackers often trick users into unknowingly running malware this way.
4. Keep your software updated: Regularly update your operating system, browsers and all software applications. Updates often include patches for security vulnerabilities that malware can exploit.
5. Use two-factor authentication (2FA): Enable 2FA on all your accounts. This adds an extra layer of security by requiring a second form of verification, making it harder for attackers to gain access even if they have your password.
6. Invest in personal data removal services: Even with strong device security, your personal information may still be exposed online through data brokers and people-finder sites. These services collect and publish details like your name, address and phone number, making you an easier target for identity theft or phishing. Automated data removal services track down these sites and submit removal requests on your behalf, helping to reduce your digital footprint and increase your online anonymity. While they can’t erase every trace of your information, they make it significantly harder for attackers to find and exploit your personal data, which saves you time and reduces unwanted spam in the process.
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
Defendnot points to a bigger issue with how Windows handles security. It takes a feature meant to prevent software conflicts and turns it into a way to completely disable protection. The system assumes any registered antivirus is legitimate, so if attackers can fake that, they get in without much resistance.
We often think of security as blocking the bad and trusting the good. But this case shows what happens when that trust is misplaced. Defendnot doesn’t sneak past Windows defenses. It walks right in using valid credentials. The solution isn’t just more patches or stronger malware signatures. What we need is a smarter way for systems to tell what is actually safe.
Do you think companies like Microsoft need to rethink how Windows handles antivirus registration and trust, given that tools like Defendnot can so easily disable built-in protections without using malware or exploiting a bug? Let us know by writing us at Cyberguy.com/Contact.
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When Oregon resident Isabelle Reksopuro heard Google was gobbling up public land to fuel its data centers in her home state, she didn’t initially know what to believe. “There’s a lot of misinformation about data centers,” she said. “Google has denied taking that land.”
Technically, she explains, The Dalles, a city near the Washington state border, sought to reclaim that land, “and Google is just a big, unnamed power user.” The city had in fact asked for ownership of a 150-acre portion of Mount Hood National Forest, claiming it needs access to Mount Hood’s watershed to meet municipal needs as its population — 16,010 as of the 2020 census — grows. But critics, including environmentalists, say the city is trying to secure more water for Google, which has a sprawling data center campus in The Dalles that already consumes about one-third of the city’s water supply.
This controversy made Reksopuro curious about the backlash to data centers being built in other communities. So Reksopuro, a student at the University of Washington who studies the connections between tech and public policy, decided to map it out. Using information collected by Epoch AI and data scraped from legislation on data centers, she built an interactive map tracking AI policy around the world. She designed it to be simple enough for anyone to use. “I wanted it to be something that my younger sisters could play through and explore to understand what are the data centers in the area and what’s actually being done about it,” Reksopuro said. She hoped to shift their opinions that way, “instead of like, through TikTok.”
Four times a day, the map searches for new sources and checks them against the existing database Reksopuro built out. “Once it does that, it will write a new summary, add it to the news feed, and populate it on the sidebar,” she said. “I wanted it to be self-updating, since I’m also a student.”
Reksopuro isn’t against data centers, but she thinks tech giants benefit from a lack of transparency around data center policies. “Right now, it’s this really opaque thing — and all of a sudden, there’s a facility,” she said. “I think that if people knew about data centers beforehand, it would give them leverage. They would be able to negotiate: ask for job training programs, tax revenue, environmental monitoring, things to improve their community.”
UCF commencement speaker Gloria Caulfield (University of Central Florida via Storyful)
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Microsoft Edge is adding a new feature that will allow its Copilot AI chatbot to gather information from all of your open tabs. When you start a conversation with Copilot, you can ask the chatbot questions about what’s in your tabs, compare the products you’re looking at, summarize your open articles, and more.
In its announcement, Microsoft says you can “select which experiences you want or leave off the ones you don’t.” The company is retiring Copilot Mode as well, which could similarly draw information from your tabs but offered some agentic features, like the ability to book a reservation on your behalf. Microsoft has since folded these agentic capabilities into its “Browse with Copilot” tool.
Several other AI features are coming to Edge, including an AI-powered “Study and Learn” mode that can turn the article you’re looking at into a study session or interactive quiz. There’s a new tool that turns your tabs into AI-powered podcasts as well, similar to what you’d find on NotebookLM, and an AI writing assistant that will pop up when you start entering text on a webpage.
You can also give Copilot permission to access your browsing history to provide more “relevant, high-quality answers,” according to Microsoft. Copilot in Edge on desktop and mobile will come with “long-term memory” as well, which can tailor its responses based on your previous conversations. And, when you open up a new tab, you’ll see a redesigned page that combines chat, search, and web navigation, along with the Journeys feature, which uses AI to organize your browsing history into categories that you can revisit.
Meanwhile, an update to Edge’s mobile app will allow you to share your screen with Copilot and talk through the questions about what you’re seeing. Microsoft says you’ll see “clear visual cues” when Copilot is active, “so you know when it’s taking an action, helping, listening, or viewing.”
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