Fake CAPTCHAs Trick Staff Into Running Malware

Help Net Security · Medium sophistication
Last updated October 15, 2026

Barracuda reports attackers are abusing fake CAPTCHA pages as a “trust step” to push victims into credential theft, malware downloads, and enabling malicious browser notifications. In some “ClickFix” variants, the CAPTCHA flow tricks users into pasting and running a command on their own Windows device, which then starts the infection.

Key findings

  • Barracuda observed CAPTCHA abuse in a large portion of phishing-kit attacks it reviewed in 2025.
  • A common flow uses an email lure (document/invoice/contract) that leads to a CAPTCHA gate and then to a fake Microsoft 365 sign-in page to steal credentials.
  • Some campaigns use fake CAPTCHAs to trigger malware downloads or to persuade users to enable browser notifications for follow-on malicious content.
  • ClickFix-style fake CAPTCHA pages can copy a command to the clipboard and then instruct the user to paste/run it, initiating infection.
  • Attackers may chain multiple brand impersonations (e.g., CAPTCHA → Adobe-style prompt → Microsoft sign-in) to resemble normal workplace steps.

Who’s being targeted

  • Commonly targeted roles: All employees, Finance and Accounts Payable, Procurement, Legal, Executive assistants, IT helpdesk (for user reporting/triage).
  • Affected industries: Cross-industry (any organization using email, document sharing, and Microsoft 365).
  • Attack channels: email, website.
  • Impersonated: Document sharing/workplace portal leading to Microsoft 365 sign-in, Fake CAPTCHA / fake browser or document error page, Website presenting a CAPTCHA or access gate.

Awareness takeaways

  • Treat unexpected CAPTCHAs as a warning sign, especially when they appear before viewing an invoice, contract, or shared file.
  • Never run commands or “fix steps” provided by a webpage, report it to IT/Security instead.
  • Watch for brand-impersonation chains (CAPTCHA → Adobe-like prompt → Microsoft sign-in) designed to feel like normal work steps.
  • Verify the website address before entering credentials or following instructions, and be cautious of misspellings or odd subdomains.

Red flags to watch for

  • Unexpected CAPTCHA gate before viewing a routine document
  • Sign-in page is a “counterfeit Microsoft 365 login page”
  • Pressure to proceed to avoid “account suspension or data loss” themes
  • A webpage instructs you to run a command on your computer
  • The site copies text to clipboard without clear permission/need
  • “Recovery instructions” that involve system tools for a simple CAPTCHA
  • CAPTCHA/access page asks to enable browser notifications
  • Unexpected prompts to allow notifications on a document/invoice page
  • Follow-on “further malicious content” delivered via notifications
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Read the video transcript

You click an invoice link, and before anything loads, boom, full-page CAPTCHA: “Verify to view document.” That fake CAPTCHA is the trust trick. After you click it, you land on a counterfeit Microsoft 365 sign-in, sometimes even after an Adobe-style prompt, built to steal your password. The nastier ClickFix versions go further: you click 'Verify', it silently copies a command, then tells you, step-by-step, to open Windows Run, paste, and hit Enter, so you infect yourself. If a ‘CAPTCHA’ leads to a login page or tells you to run a command, stop. Close it and report it to IT or Security, don’t click, don’t paste, just report.

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