@itlandytech: Beyond Phishing: How Hackers Use Fake CAPTCHAs and "Cache Smuggling" to Silently Drop Malware If a website asks you to verify you are human by pressing Win + R, Ctrl + V, and Enter—close the tab immediately. A dangerous evolution of the ClickFix social engineering tactic combines fake verification pages with Browser Cache Smuggling. 🚨 How the Attack Works * Pre-Staging (Cache Smuggling): While the victim views a compromised site, JavaScript silently fetches a malicious file disguised as a standard .png image. The browser saves it directly to local disk cache, bypassing security scanners since no active file "download" is triggered. * Clipboard Hijacking: Clicking the verification box copies a hidden, malicious command to the user's clipboard. * User Execution: The user pastes and runs the command in the Windows Run dialog (Win+R). * Local Payload Extraction: Since Run commands are limited to 260 characters, the script doesn't fetch anything new—it scans the local browser cache directory for a file matching a precise byte size, renames it, and executes it via wscript.exe. 🛠️ Execution & Impact * In-Memory Compilation: The initial script uses WMI to gather host info, fetches secondary stages, and compiles payload code on the fly using native Windows tools (csc.exe) injected into standard processes like timeout.exe. * Credential Theft: Targets passwords stored in browsers and on the device. * Persistence: Sets PowerShell execution policy to Bypass, drops Python using tar.exe, and registers a scheduled task to survive reboots. 🛡️ Key Takeaways for Security Teams * Educate Users: Legitimate CAPTCHAs run inside the web page—they will never ask you to open a system prompt, terminal, or run clipboard text. * Monitor Behavioral Indicators: Configure EDR alerts for non-standard processes (e.g., wscript.exe or PowerShell) accessing browser cache folders. * Logging: Turn on PowerShell script-block logging to capture obfuscated payload execution. #CyberSecurity #ClickFix #CacheSmuggling #InfoSec #Malware

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Sunday 04 October 2026 14:53:31 GMT